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Møller R, Pressler T, Qvist T. Antimicrobial Strategies for Cystic Fibrosis. Semin Respir Crit Care Med 2023; 44:297-306. [PMID: 36535665 DOI: 10.1055/s-0042-1758733] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Lung infection is the leading cause of death in cystic fibrosis (CF), and antimicrobial therapies are the backbone of infection management. While many different strategies may be applied, rigorous microbiological surveillance, intensive eradication therapy, and long-term maintenance therapy based on inhaled antibiotics may be considered the main strategy for infection control in individuals with CF. While most of the existing evidence is based on infection with Pseudomonas aeruginosa, other important pathogens causing lung inflammation and deterioration exist and should be treated despite the evidence gap. In this chapter, we describe the approaches to the antimicrobial treatment of the most important pathogens in CF and the evidence behind.
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Affiliation(s)
- Rikke Møller
- Department of Infectious Diseases, Cystic Fibrosis Center Copenhagen, Rigshospitalet, Copenhagen University, Copenhagen, Denmark
| | - Tacjana Pressler
- Department of Infectious Diseases, Cystic Fibrosis Center Copenhagen, Rigshospitalet, Copenhagen University, Copenhagen, Denmark
| | - Tavs Qvist
- Department of Infectious Diseases, Cystic Fibrosis Center Copenhagen, Rigshospitalet, Copenhagen University, Copenhagen, Denmark
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2
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Guillaume O, Butnarasu C, Visentin S, Reimhult E. Interplay between biofilm microenvironment and pathogenicity of Pseudomonas aeruginosa in cystic fibrosis lung chronic infection. Biofilm 2022; 4:100089. [PMID: 36324525 PMCID: PMC9618985 DOI: 10.1016/j.bioflm.2022.100089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 10/14/2022] [Accepted: 10/17/2022] [Indexed: 11/07/2022] Open
Abstract
Pseudomonas aeruginosa (PA) is a highly, if not the most, versatile microorganism capable of colonizing diverse environments. One of the niches in which PA is able to thrive is the lung of cystic fibrosis (CF) patients. Due to a genetic aberration, the lungs of CF-affected patients exhibit impaired functions, rendering them highly susceptible to bacterial colonization. Once PA attaches to the epithelial surface and transitions to a mucoid phenotype, the infection becomes chronic, and antibiotic treatments become inefficient. Due to the high number of affected people and the severity of this infection, CF-chronic infection is a well-documented disease. Still, numerous aspects of PA CF infection remain unclear. The scientific reports published over the last decades have stressed how PA can adapt to CF microenvironmental conditions and how its surrounding matrix of extracellular polymeric substances (EPS) plays a key role in its pathogenicity. In this context, it is of paramount interest to present the nature of the EPS together with the local CF-biofilm microenvironment. We review how the PA biofilm microenvironment interacts with drugs to contribute to the pathogenicity of CF-lung infection. Understanding why so many drugs are inefficient in treating CF chronic infection while effectively treating planktonic PA is essential to devising better therapeutic targets and drug formulations.
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Affiliation(s)
- Olivier Guillaume
- 3D Printing and Biofabrication Group, Institute of Materials Science and Technology, TU Wien (Technische Universität Wien), Getreidemarkt 9/308, 1060, Vienna, Austria,Austrian Cluster for Tissue Regeneration, Austria,Corresponding author. 3D Printing and Biofabrication Group, Institute of Materials Science and Technology, TU Wien (Technische Universität Wien), Getreidemarkt 9/308, 1060, Vienna, Austria.
| | - Cosmin Butnarasu
- Department of Molecular Biotechnology and Health Science, University of Turin, Turin, 10135, Italy
| | - Sonja Visentin
- Department of Molecular Biotechnology and Health Science, University of Turin, Turin, 10135, Italy
| | - Erik Reimhult
- Institute of Biologically Inspired Materials, Department of Nanobiotechnology, University of Natural Resources and Life Sciences Vienna, Muthgasse 11, 1190, Vienna, Austria
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3
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Sindeldecker D, Stoodley P. The many antibiotic resistance and tolerance strategies of Pseudomonas aeruginosa. Biofilm 2021; 3:100056. [PMID: 34471871 PMCID: PMC8387898 DOI: 10.1016/j.bioflm.2021.100056] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 08/17/2021] [Accepted: 08/18/2021] [Indexed: 12/15/2022] Open
Abstract
Pseudomonas aeruginosa is a bacterial pathogen associated with a wide range of infections and utilizes several strategies to establish and maintain infection including biofilm production, multidrug resistance, and antibiotic tolerance. Multidrug resistance in P. aeruginosa, as well as in all other bacterial pathogens, is a growing concern. Aminoglycoside resistance, in particular, is a major concern in P. aeruginosa infections and must be better understood in order to maintain effective clinical treatment. In this review, the various antibiotic resistance and tolerance mechanisms of Pseudomonas are explored including: classic mutation driven resistance, adaptive resistance, persister cells, small colony variants, phoenix colonies, and biofilms. It is important to further characterize each of these phenotypes and continue to evaluate antibiotic surviving isolates for novel driving mechanisms, so that we are better prepared to combat the rising number of recurrent and recalcitrant infections.
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Affiliation(s)
- Devin Sindeldecker
- Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH, USA
- Biomedical Sciences Graduate Program, The Ohio State University, Columbus, OH, USA
| | - Paul Stoodley
- Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH, USA
- Department of Orthopaedics, The Ohio State University, Columbus, OH, USA
- National Center for Advanced Tribology at Southampton (nCATS), Mechanical Engineering, University of Southampton, Southampton, UK
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4
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Blankenship CM, Hunter LL, Feeney MP, Cox M, Bittinger L, Garinis AC, Lin L, McPhail G, Clancy JP. Functional Impacts of Aminoglycoside Treatment on Speech Perception and Extended High-Frequency Hearing Loss in a Pediatric Cystic Fibrosis Cohort. Am J Audiol 2021; 30:834-853. [PMID: 33465313 DOI: 10.1044/2020_aja-20-00059] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Purpose The purpose of this study is to better understand the prevalence of ototoxicity-related hearing loss and its functional impact on communication in a pediatric and young adult cohort with cystic fibrosis (CF) and individuals without CF (controls). Method We did an observational, cross-sectional investigation of hearing function in children, teens, and young adults with CF (n = 57, M = 15.0 years) who received intravenous aminoglycoside antibiotics and age- and gender-matched controls (n = 61, M = 14.6 years). Participants completed standard and extended high-frequency audiometry, middle ear measures, speech perception tests, and a hearing and balance questionnaire. Results Individuals with CF were 3-4 times more likely to report issues with hearing, balance, and tinnitus and performed significantly poorer on speech perception tasks compared to controls. A higher prevalence of hearing loss was observed in individuals with CF (57%) compared to controls (37%). CF and control groups had similar proportions of slight and mild hearing losses; however, individuals with CF were 7.6 times more likely to have moderate and greater degrees of hearing loss. Older participants displayed higher average extended high-frequency thresholds, with no effect of age on average standard frequency thresholds. Although middle ear dysfunction has not previously been reported to be more prevalent in CF, this study showed that 16% had conductive or mixed hearing loss and higher rates of previous otitis media and pressure equalization tube surgeries compared to controls. Conclusions Individuals with CF have a higher prevalence of conductive, mixed, and sensorineural hearing loss; poorer speech-in-noise performance; and higher rates of multiple symptoms associated with otologic disorders (tinnitus, hearing difficulty, dizziness, imbalance, and otitis media) compared to controls. Accordingly, children with CF should be asked about these symptoms and receive baseline hearing assessment(s) prior to treatment with potentially ototoxic medications and at regular intervals thereafter in order to provide otologic and audiologic treatment for hearing- and ear-related problems to improve communication functioning.
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Affiliation(s)
- Chelsea M. Blankenship
- Communication Sciences Research Center, Cincinnati Children's Hospital Medical Center, OH
- Departments of Otolaryngology and Communication Sciences and Disorders, University of Cincinnati, OH
| | - Lisa L. Hunter
- Communication Sciences Research Center, Cincinnati Children's Hospital Medical Center, OH
- Departments of Otolaryngology and Communication Sciences and Disorders, University of Cincinnati, OH
| | - M. Patrick Feeney
- Oregon Hearing Research Center, Oregon Health & Science University, Portland
- National Center for Rehabilitative Auditory Research, VA Portland Health Care System, OR
| | - Madison Cox
- Communication Sciences Research Center, Cincinnati Children's Hospital Medical Center, OH
| | - Lindsey Bittinger
- Communication Sciences Research Center, Cincinnati Children's Hospital Medical Center, OH
| | - Angela C. Garinis
- Oregon Hearing Research Center, Oregon Health & Science University, Portland
- National Center for Rehabilitative Auditory Research, VA Portland Health Care System, OR
| | - Li Lin
- Research in Patient Services, Cincinnati Children's Hospital Medical Center, OH
| | - Gary McPhail
- Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, OH
| | - John P. Clancy
- Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, OH
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5
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Butler DA, Rana AP, Krapp F, Patel SR, Huang Y, Ozer EA, Hauser AR, Bulman ZP. Optimizing aminoglycoside selection for KPC-producing Klebsiella pneumoniae with the aminoglycoside-modifying enzyme (AME) gene aac(6')-Ib. J Antimicrob Chemother 2021; 76:671-679. [PMID: 33326561 DOI: 10.1093/jac/dkaa480] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 10/22/2020] [Indexed: 01/26/2023] Open
Abstract
OBJECTIVES KPC-producing Klebsiella pneumoniae (KPC-Kp) isolates commonly co-harbour the aminoglycoside-modifying enzyme (AME) gene aac(6')-Ib, which encodes an AME that can confer resistance to some of the commercially available aminoglycosides. We sought to determine the influence of AAC(6')-Ib in KPC-Kp on the pharmacodynamic activity of aminoglycosides. METHODS Six KPC-Kp clinical isolates, three with and three without aac(6')-Ib, were analysed. Using these isolates, the bacterial killing of amikacin, gentamicin and tobramycin was assessed in static time-kill experiments. The pharmacodynamic activity of the aminoglycosides was then assessed in a dynamic one-compartment infection model over 72 h using simulated human pharmacokinetics of once-daily dosing with amikacin (15 mg/kg), gentamicin (5 mg/kg) and tobramycin (5 mg/kg). RESULTS At clinically relevant aminoglycoside concentrations in time-kill experiments and the dynamic one-compartment model, gentamicin was more active than amikacin or tobramycin against the isolates harbouring aac(6')-Ib. Amikacin, gentamicin and tobramycin all showed progressively reduced bacterial killing with exposure to repeated doses against most isolates in the dynamic one-compartment model. MIC values were generally not a good predictor of gentamicin pharmacodynamic activity against KPC-Kp, but were more reliable for amikacin and tobramycin. CONCLUSIONS Gentamicin may be preferred over amikacin or tobramycin for treatment of KPC-Kp infections. However, gentamicin MICs are not a consistent predictor of its pharmacodynamic activity and unexpected treatment failures are possible.
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Affiliation(s)
- David A Butler
- University of Illinois at Chicago College of Pharmacy, Chicago, IL, USA
| | - Amisha P Rana
- University of Illinois at Chicago College of Pharmacy, Chicago, IL, USA
| | - Fiorella Krapp
- Northwestern University Feinberg School of Medicine, Chicago, IL, USA.,Instituto de Medicina Tropical Alexander von Humboldt, Universidad Peruana Cayetano, Lima, Peru
| | - Shitalben R Patel
- University of Illinois at Chicago College of Pharmacy, Chicago, IL, USA
| | - Yanqin Huang
- University of Illinois at Chicago College of Pharmacy, Chicago, IL, USA
| | - Egon A Ozer
- Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Alan R Hauser
- Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Zackery P Bulman
- University of Illinois at Chicago College of Pharmacy, Chicago, IL, USA
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6
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Heffernan AJ, Sime FB, Naicker S, Andrews K, Ellwood D, Guerra-Valero Y, Wallis S, Lipman J, Grimwood K, Roberts JA. Pharmacodynamics of once- versus twice-daily dosing of nebulized amikacin in an in vitro Hollow-Fiber Infection Model against 3 clinical isolates of Pseudomonas aeruginosa. Diagn Microbiol Infect Dis 2021; 100:115329. [PMID: 33714790 DOI: 10.1016/j.diagmicrobio.2021.115329] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 01/20/2021] [Accepted: 01/24/2021] [Indexed: 10/22/2022]
Abstract
This study aims to compare the bacterial killing of once- versus twice-daily nebulized amikacin against Pseudomonas aeruginosa and to determine the optimal duration of therapy. Three clinical P. aeruginosa isolates (amikacin MICs 2, 8, and 64 mg/L) were exposed to simulated epithelial lining fluid exposures of nebulized amikacin with dosing regimens of 400 mg and 800 mg once- or twice-daily up to 7-days using the in vitro hollow-fiber infection model. Quantitative cultures were performed. Simulated amikacin dosing regimens of 400 mg twice-daily and 800 mg once-daily achieved ≥2-log reduction in the bacterial burden within the first 24-hours of therapy for all isolates tested. No dosing regimen suppressed the emergence of amikacin resistance. No difference in bacterial killing or regrowth was observed between 3- and 7-days of amikacin. Amikacin doses of 800 mg once-daily for up to 3-days may be considered for future clinical trials.
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Affiliation(s)
- Aaron James Heffernan
- School of Medicine, Griffith University, Gold Coast, Queensland, Australia; Centre for Translational Anti-Infective Pharmacodynamics, School of Pharmacy, The University of Queensland, Brisbane, Queensland, Australia
| | - Fekade Bruck Sime
- Centre for Translational Anti-Infective Pharmacodynamics, School of Pharmacy, The University of Queensland, Brisbane, Queensland, Australia; University of Queensland Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Brisbane, Australia.
| | - Saiyuri Naicker
- Centre for Translational Anti-Infective Pharmacodynamics, School of Pharmacy, The University of Queensland, Brisbane, Queensland, Australia; University of Queensland Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Brisbane, Australia
| | - Katherine Andrews
- Griffith Institute for Drug Discovery, Griffith University, Nathan, Queensland, Australia
| | - David Ellwood
- School of Medicine, Griffith University, Gold Coast, Queensland, Australia; Gold Coast Health, Southport, Queensland, Australia
| | - Yarmarly Guerra-Valero
- University of Queensland Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Brisbane, Australia
| | - Steven Wallis
- University of Queensland Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Brisbane, Australia
| | - Jeffrey Lipman
- University of Queensland Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Brisbane, Australia; Department of Intensive Care Medicine, Royal Brisbane and Women's Hospital, Brisbane, Queensland, Australia; Division of Anaesthesiology Critical Care Emergency and Pain Medicine, Nîmes University Hospital, University of Montpellier, Nîmes France
| | - Keith Grimwood
- School of Medicine, Griffith University, Gold Coast, Queensland, Australia; Gold Coast Health, Southport, Queensland, Australia
| | - Jason Alexander Roberts
- Centre for Translational Anti-Infective Pharmacodynamics, School of Pharmacy, The University of Queensland, Brisbane, Queensland, Australia; University of Queensland Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Brisbane, Australia; Department of Intensive Care Medicine, Royal Brisbane and Women's Hospital, Brisbane, Queensland, Australia; Division of Anaesthesiology Critical Care Emergency and Pain Medicine, Nîmes University Hospital, University of Montpellier, Nîmes France.
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7
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Maiden MM, Waters CM. Triclosan depletes the membrane potential in Pseudomonas aeruginosa biofilms inhibiting aminoglycoside induced adaptive resistance. PLoS Pathog 2020; 16:e1008529. [PMID: 33125434 PMCID: PMC7657502 DOI: 10.1371/journal.ppat.1008529] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 11/11/2020] [Accepted: 09/15/2020] [Indexed: 12/18/2022] Open
Abstract
Biofilm-based infections are difficult to treat due to their inherent resistance to antibiotic treatment. Discovering new approaches to enhance antibiotic efficacy in biofilms would be highly significant in treating many chronic infections. Exposure to aminoglycosides induces adaptive resistance in Pseudomonas aeruginosa biofilms. Adaptive resistance is primarily the result of active antibiotic export by RND-type efflux pumps, which use the proton motive force as an energy source. We show that the protonophore uncoupler triclosan depletes the membrane potential of biofilm growing P. aeruginosa, leading to decreased activity of RND-type efflux pumps. This disruption results in increased intracellular accumulation of tobramycin and enhanced antimicrobial activity in vitro. In addition, we show that triclosan enhances tobramycin effectiveness in vivo using a mouse wound model. Combining triclosan with tobramycin is a new anti-biofilm strategy that targets bacterial energetics, increasing the susceptibility of P. aeruginosa biofilms to aminoglycosides.
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Affiliation(s)
- Michael M. Maiden
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America
- The BEACON Center for The Study of Evolution in Action, Michigan State University, East Lansing, Michigan, United States of America
| | - Christopher M. Waters
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America
- The BEACON Center for The Study of Evolution in Action, Michigan State University, East Lansing, Michigan, United States of America
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8
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Pharmacodynamic Evaluation of Plasma and Epithelial Lining Fluid Exposures of Amikacin against Pseudomonas aeruginosa in a Dynamic In Vitro Hollow-Fiber Infection Model. Antimicrob Agents Chemother 2020; 64:AAC.00879-20. [PMID: 32660986 DOI: 10.1128/aac.00879-20] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 07/01/2020] [Indexed: 01/14/2023] Open
Abstract
Given that aminoglycosides, such as amikacin, may be used for multidrug-resistant Pseudomonas aeruginosa infections, optimization of therapy is paramount for improved treatment outcomes. This study aims to investigate the pharmacodynamics of different simulated intravenous amikacin doses on susceptible P. aeruginosa to inform ventilator-associated pneumonia (VAP) and sepsis treatment choices. A hollow-fiber infection model with two P. aeruginosa isolates (MICs of 2 and 8 mg/liter) with an initial inoculum of ∼108 CFU/ml was used to test different amikacin dosing regimens. Three regimens (15, 25, and 50 mg/kg) were tested to simulate a blood exposure, while a 30 mg/kg regimen simulated the epithelial lining fluid (ELF) for potential respiratory tract infection. Data were described using a semimechanistic pharmacokinetic/pharmacodynamic (PK/PD) model. Whole-genome sequencing was used to identify mutations associated with resistance emergence. While bacterial density was reduced by >6 logs within the first 12 h in simulated blood exposures following this initial bacterial kill, there was amplification of a resistant subpopulation with ribosomal mutations that were likely mediating amikacin resistance. No appreciable bacterial killing occurred with subsequent doses. There was less (<5 log) bacterial killing in the simulated ELF exposure for either isolate tested. Simulation studies suggested that a dose of 30 and 50 mg/kg may provide maximal bacterial killing for bloodstream and VAP infections, respectively. Our results suggest that amikacin efficacy may be improved with the use of high-dose therapy to rapidly eliminate susceptible bacteria. Subsequent doses may have reduced efficacy given the rapid amplification of less-susceptible bacterial subpopulations with amikacin monotherapy.
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AlMatar M, Albarri O, Makky EA, Var I, Köksal F. A Glance on the Role of Bacterial Siderophore from the Perspectives of Medical and Biotechnological Approaches. Curr Drug Targets 2020; 21:1326-1343. [PMID: 32564749 DOI: 10.2174/1389450121666200621193018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 05/10/2020] [Accepted: 05/20/2020] [Indexed: 11/22/2022]
Abstract
Iron, which is described as the most basic component found in nature, is hard to be assimilated by microorganisms. It has become increasingly complicated to obtain iron from nature as iron (II) in the presence of oxygen oxidized to press (III) oxide and hydroxide, becoming unsolvable at neutral pH. Microorganisms appeared to produce organic molecules known as siderophores in order to overcome this condition. Siderophore's essential function is to connect with iron (II) and make it dissolvable and enable cell absorption. These siderophores, apart from iron particles, have the ability to chelate various other metal particles that have collocated away to focus the use of siderophores on wound care items. There is a severe clash between the host and the bacterial pathogens during infection. By producing siderophores, small ferric iron-binding molecules, microorganisms obtain iron. In response, host immune cells produce lipocalin 2 to prevent bacterial reuptake of siderophores loaded with iron. Some bacteria are thought to produce lipocalin 2-resistant siderophores to counter this risk. The aim of this article is to discuss the recently described roles and applications of bacterial siderophore.
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Affiliation(s)
- Manaf AlMatar
- Faculty of Industrial Sciences & Technology, Universiti Malaysia Pahang (UMP), Gambang, 26300 Kuantan, Malaysia
| | - Osman Albarri
- Department of Biotechnology, Institute of Natural and Applied Sciences (Fen Bilimleri Enstitusu) Cukurova University, Adana, Turkey
| | - Essam A Makky
- Faculty of Industrial Sciences & Technology, Universiti Malaysia Pahang (UMP), Gambang, 26300 Kuantan, Malaysia
| | - Işıl Var
- Department of Food Engineering, Agricultural Faculty, Cukurova University, Adana, Turkey
| | - Fatih Köksal
- Department of Medical Microbiology, Faculty of Medicine, Cukurova University, Adana, Turkey
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10
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Tewes F, Bahamondez-Canas TF, Moraga-Espinoza D, Smyth HDC, Watts AB. In vivo efficacy of a dry powder formulation of ciprofloxacin-copper complex in a chronic lung infection model of bioluminescent Pseudomonas aeruginosa. Eur J Pharm Biopharm 2020; 152:210-217. [PMID: 32442738 DOI: 10.1016/j.ejpb.2020.05.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 05/01/2020] [Accepted: 05/15/2020] [Indexed: 12/21/2022]
Abstract
A significant limitation of locally delivered treatments for chronic pulmonary infections is often the short residence time within the airways. Ciprofloxacin (CIP), for example, undergoes rapid absorption from the airway lumen. Previously, we demonstrated that the complexation of CIP with copper (CIP-Cu) reduces its apparent epithelial permeability and pulmonary absorption rate without affecting antimicrobial activity against Pseudomonas aeruginosa grown planktonically or as biofilms. This study aimed to evaluate the in vivo efficacy of CIP-Cu, prepared as a dry powder, in a chronic lung infection model. The powders were prepared by jet milling (CIP-HCl) and by spray drying (CIP-Cu). A bioluminescent strain of P. aeruginosa (PAO1::p16Slux) was used to prepare bacteria-loaded agar beads that were inoculated intratracheally to rats. The dynamics of the infection were monitored using luminometry. The bacteria/beads ratio was optimized to allow the highest luminescence signal and animal survival for 8 days. The efficacy of the treatment was evaluated by luminometry in addition to the end-point (Day 8) where colony counting was performed after lung harvesting. Luminescent P. aeruginosa entrapped in agar beads were useful to monitor the spatial development of the chronic lung infection in rats. The rats were treated with the dry powders in a nose-only inhalation exposure system (NOIES). CIP-Cu and CIP-HCl powders showed similar aerodynamic properties and comparable CIP lung deposition. However, treatment with CIP-Cu significantly (p < 0.01) reduced by 4-log the number of CFU of P. aeruginosa per lung in the chronic infection model, whereas CIP-HCl effect was not different from the untreated control group.
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Affiliation(s)
- Frédéric Tewes
- INSERM U1070, UFR de Médecine Pharmacie, Université de Poitiers, 1 rue Georges Bonnet, TSA 51106, 86073 Poitiers Cedex 9, France; College of Pharmacy, The University of Texas at Austin, 2409 West University Avenue, PHR 4.214, Austin, TX 78712, USA.
| | - Tania F Bahamondez-Canas
- College of Pharmacy, The University of Texas at Austin, 2409 West University Avenue, PHR 4.214, Austin, TX 78712, USA; Escuela de Farmacia, Universidad de Valparaiso, Gran Bretaña 1093, Playa Ancha, Valparaíso, Chile; Centro de Investigación Farmacopea, Universidad de Valparaíso, Santa Marta 183, Playa Ancha, Valparaíso, Chile
| | - Daniel Moraga-Espinoza
- College of Pharmacy, The University of Texas at Austin, 2409 West University Avenue, PHR 4.214, Austin, TX 78712, USA; Escuela de Farmacia, Universidad de Valparaiso, Gran Bretaña 1093, Playa Ancha, Valparaíso, Chile; Centro de Investigación Farmacopea, Universidad de Valparaíso, Santa Marta 183, Playa Ancha, Valparaíso, Chile
| | - Hugh D C Smyth
- College of Pharmacy, The University of Texas at Austin, 2409 West University Avenue, PHR 4.214, Austin, TX 78712, USA
| | - Alan B Watts
- College of Pharmacy, The University of Texas at Austin, 2409 West University Avenue, PHR 4.214, Austin, TX 78712, USA
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11
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Page MGP. The Role of Iron and Siderophores in Infection, and the Development of Siderophore Antibiotics. Clin Infect Dis 2019; 69:S529-S537. [PMID: 31724044 PMCID: PMC6853763 DOI: 10.1093/cid/ciz825] [Citation(s) in RCA: 120] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Iron is an essential nutrient for bacterial growth, replication, and metabolism. Humans store iron bound to various proteins such as hemoglobin, haptoglobin, transferrin, ferritin, and lactoferrin, limiting the availability of free iron for pathogenic bacteria. However, bacteria have developed various mechanisms to sequester or scavenge iron from the host environment. Iron can be taken up by means of active transport systems that consist of bacterial small molecule siderophores, outer membrane siderophore receptors, the TonB-ExbBD energy-transducing proteins coupling the outer and the inner membranes, and inner membrane transporters. Some bacteria also express outer membrane receptors for iron-binding proteins of the host and extract iron directly from these for uptake. Ultimately, iron is acquired and transported into the bacterial cytoplasm. The siderophores are small molecules produced and released by nearly all bacterial species and are classified according to the chemical nature of their iron-chelating group (ie, catechol, hydroxamate, α-hydroxyl-carboxylate, or mixed types). Siderophore-conjugated antibiotics that exploit such iron-transport systems are under development for the treatment of infections caused by gram-negative bacteria. Despite demonstrating high in vitro potency against pathogenic multidrug-resistant bacteria, further development of several candidates had stopped due to apparent adaptive resistance during exposure, lack of consistent in vivo efficacy, or emergence of side effects in the host. However, cefiderocol, with an optimized structure, has advanced and has been investigated in phase 1 to 3 clinical trials. This article discusses the mechanisms implicated in iron uptake and the challenges associated with the design and utilization of siderophore-mimicking antibiotics.
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Affiliation(s)
- Malcom G P Page
- Life Sciences and Chemistry, Jacobs University, Bremen gGmbh, Bremen, Germany
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12
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Tobramycin Promotes Melanogenesis by Upregulating p38 MAPK Protein Phosphorylation in B16F10 Melanoma Cells. Antibiotics (Basel) 2019; 8:antibiotics8030140. [PMID: 31491963 PMCID: PMC6783951 DOI: 10.3390/antibiotics8030140] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 08/28/2019] [Accepted: 09/02/2019] [Indexed: 01/27/2023] Open
Abstract
Tobramycin is an aminoglycoside-based natural antibiotic derived from Streptomyces tenebrarius, which is primarily used for Gram-negative bacterial infection treatment. Although tobramycin has been utilized in clinical practice for a long time, it has exhibited several side effects, leading to the introduction of more effective antibiotics. Therefore, we conducted our experiments focusing on new possibilities for the clinical use of tobramycin. How tobramycin affects skin melanin formation is unknown. This study used B16F10 melanoma cells to assess the effect of tobramycin on melanin production. After cytotoxicity was assessed by MTT assay, melanin content and tyrosinase activity analyses revealed that tobramycin induces melanin synthesis in B16F10 cells. Next, Western blot analyses were performed to elucidate the mechanism by which tobramycin increases melanin production; phosphorylated p38 protein expression was upregulated. Protein inhibitors have been used to elucidate the mechanism of tobramycin. Kanamycin A and B are structurally similar to tobramycin, and 2-DOS represents the central structure of these antibiotics. The effects of these substances on melanogenesis were evaluated. Kanamycin A reduced melanin production, whereas kanamycin B and 2-DOS had no effect. Overall, our data indicated that tobramycin increases melanin production by promoting p38 protein phosphorylation in B16F10 melanoma cells.
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13
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Bos AC, Mouton JW, van Westreenen M, Andrinopoulou ER, Janssens HM, Tiddens HAWM. Patient-specific modelling of regional tobramycin concentration levels in airways of patients with cystic fibrosis: can we dose once daily? J Antimicrob Chemother 2018; 72:3435-3442. [PMID: 29029057 DOI: 10.1093/jac/dkx293] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 07/18/2017] [Indexed: 01/28/2023] Open
Abstract
Background Inhaled tobramycin is important in the treatment of Pseudomonas aeruginosa (Pa) infections in cystic fibrosis (CF). However, despite its use it fails to attenuate the clinical progression of CF lung disease. The bactericidal efficacy of tobramycin is known to be concentration-dependent and hence changing the dosing regimen from a twice-daily (q12h) inhalation to a once-daily (q24h) inhaled double dose could improve treatment outcomes. Objectives To predict local concentrations of nebulized tobramycin in the airways of patients with CF, delivered with the small airway-targeting Akita® system or standard PARI-LC® Plus system, with different inspiratory flow profiles. Methods Computational fluid dynamic (CFD) methods were applied to patient-specific airway models reconstructed from chest CT scans. The following q12h and q24h dosing regimens were evaluated: Akita® (150 and 300 mg) and PARI-LC® Plus (300 and 600 mg). Site-specific concentrations were calculated. Results Twelve CT scans from patients aged 12-17 years (median = 15.7) were selected. Small airway concentrations were 762-2999 mg/L for the q12h dosing regimen and 1523-5997 mg/L for the q24h dosing regimen, well above the MIC for WT Pa strains. Importantly, the q24h regimen appeared to be more suitable than the q12h regimen against more resistant Pa strains and the inhibitory effects of sputum on tobramycin activity. Conclusions CFD modelling showed that high concentrations of inhaled tobramycin are indeed delivered to the airways, with the Akita® system being twice as efficient as the PARI-LC® system. Ultimately, the q24h dosing regimen appears more effective against subpopulations with high MICs (i.e. more resistant strains).
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Affiliation(s)
- Aukje C Bos
- Department of Pediatric Pulmonology, Erasmus Medical Centre (MC)-Sophia Children's Hospital, Wytemaweg 80, 3015 CN Rotterdam, The Netherlands.,Department of Radiology, Erasmus MC, Wytemaweg 80, 3015 CN Rotterdam, The Netherlands
| | - Johan W Mouton
- Department of Medical Microbiology and Infectious Diseases, Erasmus MC, Wytemaweg 80, 3015 CN Rotterdam, The Netherlands
| | - Mireille van Westreenen
- Department of Medical Microbiology and Infectious Diseases, Erasmus MC, Wytemaweg 80, 3015 CN Rotterdam, The Netherlands
| | | | - Hettie M Janssens
- Department of Pediatric Pulmonology, Erasmus Medical Centre (MC)-Sophia Children's Hospital, Wytemaweg 80, 3015 CN Rotterdam, The Netherlands
| | - Harm A W M Tiddens
- Department of Pediatric Pulmonology, Erasmus Medical Centre (MC)-Sophia Children's Hospital, Wytemaweg 80, 3015 CN Rotterdam, The Netherlands.,Department of Radiology, Erasmus MC, Wytemaweg 80, 3015 CN Rotterdam, The Netherlands
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14
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15
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Tai AS, Sherrard LJ, Kidd TJ, Ramsay KA, Buckley C, Syrmis M, Grimwood K, Bell SC, Whiley DM. Antibiotic perturbation of mixed-strain Pseudomonas aeruginosa infection in patients with cystic fibrosis. BMC Pulm Med 2017; 17:138. [PMID: 29096618 PMCID: PMC5667482 DOI: 10.1186/s12890-017-0482-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 10/25/2017] [Indexed: 12/20/2022] Open
Abstract
Background Pulmonary exacerbations in cystic fibrosis (CF) remain poorly understood and treatment is usually targeted at Pseudomonas aeruginosa. Within Australia a predominant shared P. aeruginosa strain (AUST-02) is associated with greater treatment needs. This single centre study assessed temporal shared strain population dynamics during and after antibiotic treatment of exacerbations. Methods Sputum was collected from 12 adult patients with a history of chronic AUST-02 infection at four time-points during and after treatment of an exacerbation. Forty-eight P. aeruginosa isolates within each sample underwent AUST-02 allele-specific PCR and SNP-based strain genotyping. Results Various commonly shared Australian strains (AUST-01, 0.1%; AUST-02, 54.3%; AUST-06, 36.6%; AUST-07, 4.6%; AUST-11, 4.3%) and two unique strains (0.1%) were identified from 45 sputum samples (2160 isolates). Based on within-patient relative abundance of strains, a “single-strain infection” (n = 7) or “mixed-strain infection” (n = 5) was assigned to each patient. A significant temporal variation in the P. aeruginosa population composition was found for those with mixed-strain infection (P < 0.001). Patients with mixed-strain infections had more long-term treatment requirements than those with single-strain infection. Moreover, despite both groups having similar lung function at study entry, patients with single-strain infection had greater improvement in FEV1% predicted following their exacerbation treatment (P = 0.02). Conclusion Pulmonary exacerbations may reveal multiple, unrelated P. aeruginosa strains whose relative abundance with one another may change rapidly, in a sustained and unpredictable manner. Electronic supplementary material The online version of this article (10.1186/s12890-017-0482-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Anna S Tai
- School of Medicine, The University of Queensland, Brisbane, QLD, Australia. .,Adult Cystic Fibrosis Centre, Department of Thoracic Medicine, The Prince Charles Hospital, Brisbane, QLD, Australia. .,Western Australia Adult Cystic Fibrosis Centre, Department of Respiratory Medicine, Sir Charles Gairdner Hospital, Hospital Avenue, Perth, WA, 6009, Australia.
| | - Laura J Sherrard
- Lung Bacteria Group, QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia
| | - Timothy J Kidd
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia.,Centre for Experimental Medicine, Queen's University Belfast, Belfast, UK.,Child Health Research Centre, The University of Queensland, Brisbane, QLD, Australia
| | - Kay A Ramsay
- School of Medicine, The University of Queensland, Brisbane, QLD, Australia.,Lung Bacteria Group, QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia
| | - Cameron Buckley
- UQ Centre for Clinical Research, The University of Queensland, Brisbane, QLD, Australia
| | - Melanie Syrmis
- UQ Centre for Clinical Research, The University of Queensland, Brisbane, QLD, Australia.,Pathology Queensland, Microbiology Department, Brisbane, QLD, Australia
| | - Keith Grimwood
- Child Health Research Centre, The University of Queensland, Brisbane, QLD, Australia.,Menzies Health Institute Queensland, Griffith University and Gold Coast Health, Gold Coast, QLD, Australia
| | - Scott C Bell
- Adult Cystic Fibrosis Centre, Department of Thoracic Medicine, The Prince Charles Hospital, Brisbane, QLD, Australia.,Lung Bacteria Group, QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia
| | - David M Whiley
- UQ Centre for Clinical Research, The University of Queensland, Brisbane, QLD, Australia.,Pathology Queensland, Microbiology Department, Brisbane, QLD, Australia
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16
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Inhibition of Pseudomonas aeruginosa by Peptide-Conjugated Phosphorodiamidate Morpholino Oligomers. Antimicrob Agents Chemother 2017; 61:AAC.01938-16. [PMID: 28137807 DOI: 10.1128/aac.01938-16] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Accepted: 01/09/2017] [Indexed: 01/01/2023] Open
Abstract
Pseudomonas aeruginosa is a highly virulent, multidrug-resistant pathogen that causes significant morbidity and mortality in hospitalized patients and is particularly devastating in patients with cystic fibrosis. Increasing antibiotic resistance coupled with decreasing numbers of antibiotics in the developmental pipeline demands novel antibacterial approaches. Here, we tested peptide-conjugated phosphorodiamidate morpholino oligomers (PPMOs), which inhibit translation of complementary mRNA from specific, essential genes in P. aeruginosa PPMOs targeted to acpP, lpxC, and rpsJ, inhibited P. aeruginosa growth in many clinical strains and activity of PPMOs could be enhanced 2- to 8-fold by the addition of polymyxin B nonapeptide at subinhibitory concentrations. The PPMO targeting acpP was also effective at preventing P. aeruginosa PAO1 biofilm formation and at reducing existing biofilms. Importantly, treatment with various combinations of a PPMO and a traditional antibiotic demonstrated synergistic growth inhibition, the most effective of which was the PPMO targeting rpsJ with tobramycin. Furthermore, treatment of P. aeruginosa PA103-infected mice with PPMOs targeting acpP, lpxC, or rpsJ significantly reduced the bacterial burden in the lungs at 24 h by almost 3 logs. Altogether, this study demonstrates that PPMOs targeting the essential genes acpP, lpxC, or rpsJ in P. aeruginosa are highly effective at inhibiting growth in vitro and in vivo These data suggest that PPMOs alone or in combination with antibiotics represent a novel approach to addressing the problems associated with rapidly increasing antibiotic resistance in P. aeruginosa.
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17
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Abstract
Resistance to antibiotics is an important and timely problem of contemporary medicine. Rapid evolution of resistant bacteria calls for new preventive measures to slow down this process, and a longer-term progress cannot be achieved without a good understanding of the mechanisms through which drug resistance is acquired and spreads in microbial populations. Here, we discuss recent experimental and theoretical advances in our knowledge how the dynamics of microbial populations affects the evolution of antibiotic resistance . We focus on the role of spatial and temporal drug gradients and show that in certain situations bacteria can evolve de novo resistance within hours. We identify factors that lead to such rapid onset of resistance and discuss their relevance for bacterial infections.
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18
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Herzog IM, Louzoun Zada S, Fridman M. Effects of 5-O-Ribosylation of Aminoglycosides on Antimicrobial Activity and Selective Perturbation of Bacterial Translation. J Med Chem 2016; 59:8008-18. [PMID: 27509271 DOI: 10.1021/acs.jmedchem.6b00793] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
We studied six pairs of aminoglycosides and their corresponding ribosylated derivatives synthesized by attaching a β-O-linked ribofuranose to the 5-OH of the deoxystreptamine ring of the parent pseudo-oligosaccharide antibiotic. Ribosylation of the 4,6-disubstituted 2-deoxystreptamine aminoglycoside kanamycin B led to improved selectivity for inhibition of prokaryotic relative to cytosolic eukaryotic in vitro translation. For the pseudodisaccharide aminoglycoside scaffolds neamine and nebramine, ribosylated derivatives were both more potent antimicrobials and more selective to inhibition of prokaryotic translation. On the basis of the results of this study, we suggest that modification of the 5-OH position of the streptamine ring of other natural or semisynthetic pseudodisaccharide aminoglycoside scaffolds containing an equatorial amine at the 2' sugar position with a β-O-linked ribofuranose is a promising avenue for the development of novel aminoglycoside antibiotics with improved efficacy and reduced toxicity.
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Affiliation(s)
- Ido M Herzog
- School of Chemistry, Raymond and Beverley Sackler Faculty of Exact Sciences, Tel Aviv University , Tel Aviv 6997801, Israel
| | - Sivan Louzoun Zada
- School of Chemistry, Raymond and Beverley Sackler Faculty of Exact Sciences, Tel Aviv University , Tel Aviv 6997801, Israel
| | - Micha Fridman
- School of Chemistry, Raymond and Beverley Sackler Faculty of Exact Sciences, Tel Aviv University , Tel Aviv 6997801, Israel
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19
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Valentini M, Filloux A. Biofilms and Cyclic di-GMP (c-di-GMP) Signaling: Lessons from Pseudomonas aeruginosa and Other Bacteria. J Biol Chem 2016; 291:12547-12555. [PMID: 27129226 PMCID: PMC4933438 DOI: 10.1074/jbc.r115.711507] [Citation(s) in RCA: 341] [Impact Index Per Article: 42.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The cyclic di-GMP (c-di-GMP) second messenger represents a signaling system that regulates many bacterial behaviors and is of key importance for driving the lifestyle switch between motile loner cells and biofilm formers. This review provides an up-to-date compendium of c-di-GMP pathways connected to biofilm formation, biofilm-associated motilities, and other functionalities in the ubiquitous and opportunistic human pathogen Pseudomonas aeruginosa This bacterium is frequently adopted as a model organism to study bacterial biofilm formation. Importantly, its versatility and adaptation capabilities are linked with a broad range of complex regulatory networks, including a large set of genes involved in c-di-GMP biosynthesis, degradation, and transmission.
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Affiliation(s)
- Martina Valentini
- MRC Centre for Molecular Microbiology and Infection, Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom.
| | - Alain Filloux
- MRC Centre for Molecular Microbiology and Infection, Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom.
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20
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Kamath KS, Pascovici D, Penesyan A, Goel A, Venkatakrishnan V, Paulsen IT, Packer NH, Molloy MP. Pseudomonas aeruginosa Cell Membrane Protein Expression from Phenotypically Diverse Cystic Fibrosis Isolates Demonstrates Host-Specific Adaptations. J Proteome Res 2016; 15:2152-63. [PMID: 27246823 DOI: 10.1021/acs.jproteome.6b00058] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Pseudomonas aeruginosa is a Gram-negative, nosocomial, highly adaptable opportunistic pathogen especially prevalent in immuno-compromised cystic fibrosis (CF) patients. The bacterial cell surface proteins are important contributors to virulence, yet the membrane subproteomes of phenotypically diverse P. aeruginosa strains are poorly characterized. We carried out mass spectrometry (MS)-based proteome analysis of the membrane proteins of three novel P. aeruginosa strains isolated from the sputum of CF patients and compared protein expression to the widely used laboratory strain, PAO1. Microbes were grown in planktonic growth condition using minimal M9 media, and a defined synthetic lung nutrient mimicking medium (SCFM) limited passaging. Two-dimensional LC-MS/MS using iTRAQ labeling enabled quantitative comparisons among 3171 and 2442 proteins from the minimal M9 medium and in the SCFM, respectively. The CF isolates showed marked differences in membrane protein expression in comparison with PAO1 including up-regulation of drug resistance proteins (MexY, MexB, MexC) and down-regulation of chemotaxis and aerotaxis proteins (PA1561, PctA, PctB) and motility and adhesion proteins (FliK, FlgE, FliD, PilJ). Phenotypic analysis using adhesion, motility, and drug susceptibility assays confirmed the proteomics findings. These results provide evidence of host-specific microevolution of P. aeruginosa in the CF lung and shed light on the adaptation strategies used by CF pathogens.
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Affiliation(s)
- Karthik Shantharam Kamath
- Department of Chemistry and Biomolecular Sciences, Macquarie University , Sydney, New South Wales 2109, Australia
| | - Dana Pascovici
- Australian Proteome Analysis Facility, Macquarie University , Sydney, New South Wales 2109, Australia
| | - Anahit Penesyan
- Department of Chemistry and Biomolecular Sciences, Macquarie University , Sydney, New South Wales 2109, Australia
| | - Apurv Goel
- Australian Proteome Analysis Facility, Macquarie University , Sydney, New South Wales 2109, Australia
| | - Vignesh Venkatakrishnan
- Department of Chemistry and Biomolecular Sciences, Macquarie University , Sydney, New South Wales 2109, Australia
| | - Ian T Paulsen
- Department of Chemistry and Biomolecular Sciences, Macquarie University , Sydney, New South Wales 2109, Australia
| | - Nicolle H Packer
- Department of Chemistry and Biomolecular Sciences, Macquarie University , Sydney, New South Wales 2109, Australia
| | - Mark P Molloy
- Department of Chemistry and Biomolecular Sciences, Macquarie University , Sydney, New South Wales 2109, Australia.,Australian Proteome Analysis Facility, Macquarie University , Sydney, New South Wales 2109, Australia
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21
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Taneja N, Kaur H. Insights into Newer Antimicrobial Agents Against Gram-negative Bacteria. Microbiol Insights 2016; 9:9-19. [PMID: 27013887 PMCID: PMC4803319 DOI: 10.4137/mbi.s29459] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 01/04/2016] [Accepted: 01/11/2016] [Indexed: 02/06/2023] Open
Abstract
Currently, drug resistance, especially against cephalosporins and carbapenems, among gram-negative bacteria is an important challenge, which is further enhanced by the limited availability of drugs against these bugs. There are certain antibiotics (colistin, fosfomycin, temocillin, and rifampicin) that have been revived from the past to tackle the menace of superbugs, including members of Enterobacteriaceae, Acinetobacter species, and Pseudomonas species. Very few newer antibiotics have been added to the pool of existing drugs. There are still many antibiotics that are passing through various phases of clinical trials. The initiative of Infectious Disease Society of America to develop 10 novel antibiotics against gram-negative bacilli by 2020 is a step to fill the gap of limited availability of drugs. This review aims to provide insights into the current and newer drugs in pipeline for the treatment of gram-negative bacteria and also discusses the major challenging issues for their management.
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Affiliation(s)
- Neelam Taneja
- Department of Medical Microbiology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
| | - Harsimran Kaur
- Department of Medical Microbiology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
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22
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Kim A, Kutschke A, Ehmann DE, Patey SA, Crandon JL, Gorseth E, Miller AA, McLaughlin RE, Blinn CM, Chen A, Nayar AS, Dangel B, Tsai AS, Rooney MT, Murphy-Benenato KE, Eakin AE, Nicolau DP. Pharmacodynamic Profiling of a Siderophore-Conjugated Monocarbam in Pseudomonas aeruginosa: Assessing the Risk for Resistance and Attenuated Efficacy. Antimicrob Agents Chemother 2015; 59:7743-52. [PMID: 26438502 PMCID: PMC4649189 DOI: 10.1128/aac.00831-15] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Accepted: 09/29/2015] [Indexed: 01/05/2023] Open
Abstract
The objective of this study was to investigate the risk of attenuated efficacy due to adaptive resistance for the siderophore-conjugated monocarbam SMC-3176 in Pseudomonas aeruginosa by using a pharmacokinetic/pharmacodynamic (PK/PD) approach. MICs were determined in cation-adjusted Mueller-Hinton broth (MHB) and in Chelex-treated, dialyzed MHB (CDMHB). Spontaneous resistance was assessed at 2× to 16× the MIC and the resulting mutants sequenced. Efficacy was evaluated in a neutropenic mouse thigh model at 3.13 to 400 mg/kg of body weight every 3 h for 24 h and analyzed for association with free time above the MIC (fT>MIC). To closer emulate the conditions of the in vivo model, we developed a novel assay testing activity mouse whole blood (WB). All mutations were found in genes related to iron uptake: piuA, piuC, pirR, fecI, and pvdS. Against four P. aeruginosa isolates, SMC-3176 displayed predictable efficacy corresponding to the fT>MIC using the MIC in CDMHB (R(2) = 0.968 to 0.985), with stasis to 2-log kill achieved at 59.4 to 81.1%. Efficacy did not translate for P. aeruginosa isolate JJ 4-36, as the in vivo responses were inconsistent with fT>MIC exposures and implied a threshold concentration that was greater than the MIC. The results of the mouse WB assay indicated that efficacy was not predictable using the MIC for JJ 4-36 and four additional isolates, against which in vivo failures of another siderophore-conjugated β-lactam were previously reported. SMC-3176 carries a risk of attenuated efficacy in P. aeruginosa due to rapid adaptive resistance preventing entry via the siderophore-mediated iron uptake systems. Substantial in vivo testing is warranted for compounds using the siderophore approach to thoroughly screen for this in vitro-in vivo disconnect in P. aeruginosa.
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Affiliation(s)
- Aryun Kim
- Infection Innovative Medicines, AstraZeneca Pharmaceuticals LP, Waltham, Massachusetts, USA
| | - Amy Kutschke
- Infection Innovative Medicines, AstraZeneca Pharmaceuticals LP, Waltham, Massachusetts, USA
| | - David E Ehmann
- Infection Innovative Medicines, AstraZeneca Pharmaceuticals LP, Waltham, Massachusetts, USA
| | - Sara A Patey
- Infection Innovative Medicines, AstraZeneca Pharmaceuticals LP, Waltham, Massachusetts, USA
| | - Jared L Crandon
- Center for Anti-Infective Research and Development, Hartford Hospital, Hartford, Connecticut, USA
| | - Elise Gorseth
- Infection Innovative Medicines, AstraZeneca Pharmaceuticals LP, Waltham, Massachusetts, USA
| | - Alita A Miller
- Infection Innovative Medicines, AstraZeneca Pharmaceuticals LP, Waltham, Massachusetts, USA
| | - Robert E McLaughlin
- Infection Innovative Medicines, AstraZeneca Pharmaceuticals LP, Waltham, Massachusetts, USA
| | - Christina M Blinn
- Infection Innovative Medicines, AstraZeneca Pharmaceuticals LP, Waltham, Massachusetts, USA
| | - April Chen
- Infection Innovative Medicines, AstraZeneca Pharmaceuticals LP, Waltham, Massachusetts, USA
| | - Asha S Nayar
- Infection Innovative Medicines, AstraZeneca Pharmaceuticals LP, Waltham, Massachusetts, USA
| | - Brian Dangel
- Infection Innovative Medicines, AstraZeneca Pharmaceuticals LP, Waltham, Massachusetts, USA
| | - Andy S Tsai
- Infection Innovative Medicines, AstraZeneca Pharmaceuticals LP, Waltham, Massachusetts, USA
| | - Michael T Rooney
- Infection Innovative Medicines, AstraZeneca Pharmaceuticals LP, Waltham, Massachusetts, USA
| | | | - Ann E Eakin
- Infection Innovative Medicines, AstraZeneca Pharmaceuticals LP, Waltham, Massachusetts, USA
| | - David P Nicolau
- Center for Anti-Infective Research and Development, Hartford Hospital, Hartford, Connecticut, USA
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23
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Clark ST, Diaz Caballero J, Cheang M, Coburn B, Wang PW, Donaldson SL, Zhang Y, Liu M, Keshavjee S, Yau YC, Waters VJ, Elizabeth Tullis D, Guttman DS, Hwang DM. Phenotypic diversity within a Pseudomonas aeruginosa population infecting an adult with cystic fibrosis. Sci Rep 2015; 5:10932. [PMID: 26047320 PMCID: PMC4456944 DOI: 10.1038/srep10932] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Accepted: 05/05/2015] [Indexed: 01/05/2023] Open
Abstract
Chronic airway infections caused by Pseudomonas aeruginosa contribute to the progression of pulmonary disease in individuals with cystic fibrosis (CF). In the setting of CF, within-patient adaptation of a P. aeruginosa strain generates phenotypic diversity that can complicate microbiological analysis of patient samples. We investigated within- and between- sample diversity of 34 phenotypes among 235 P. aeruginosa isolates cultured from sputum samples collected from a single CF patient over the span of one year, and assessed colony morphology as a screening tool for predicting phenotypes, including antimicrobial susceptibilities. We identified 15 distinct colony morphotypes that varied significantly in abundance both within and between sputum samples. Substantial within sample phenotypic heterogeneity was also noted in other phenotypes, with morphotypes being unreliable predictors of antimicrobial susceptibility and other phenotypes. Emergence of isolates with reduced susceptibility to β-lactams was observed during periods of clinical therapy with aztreonam. Our findings confirm that the P. aeruginosa population in chronic CF lung infections is highly dynamic, and that intra-sample phenotypic diversity is underestimated if only one or few colonies are analyzed per sample.
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Affiliation(s)
- Shawn T. Clark
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada
- Latner Thoracic Surgery Research Laboratories, University Health Network, Toronto, Canada
| | | | - Mary Cheang
- Latner Thoracic Surgery Research Laboratories, University Health Network, Toronto, Canada
| | - Bryan Coburn
- Department of Cell & Systems Biology, University of Toronto, Toronto, Canada
| | - Pauline W. Wang
- Department of Cell & Systems Biology, University of Toronto, Toronto, Canada
- Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, Canada
| | - Sylva L. Donaldson
- Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, Canada
| | - Yu Zhang
- Latner Thoracic Surgery Research Laboratories, University Health Network, Toronto, Canada
| | - Mingyao Liu
- Latner Thoracic Surgery Research Laboratories, University Health Network, Toronto, Canada
| | - Shaf Keshavjee
- Latner Thoracic Surgery Research Laboratories, University Health Network, Toronto, Canada
| | - Yvonne C.W. Yau
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada
- Department of Pediatric Laboratory Medicine, Division of Microbiology, The Hospital for Sick Children, Toronto, Canada
| | - Valerie J. Waters
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada
- Department of Pediatrics, Division of Infectious Diseases, The Hospital for Sick Children, Toronto, Canada
| | - D. Elizabeth Tullis
- Department of Medicine, Division of Respirology, St. Michael’s Hospital, Toronto, Canada
| | - David S. Guttman
- Department of Cell & Systems Biology, University of Toronto, Toronto, Canada
- Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, Canada
| | - David M. Hwang
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada
- Latner Thoracic Surgery Research Laboratories, University Health Network, Toronto, Canada
- Laboratory Medicine Program, University Health Network, Toronto, Canada
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24
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Wu X, Held K, Zheng C, Staudinger BJ, Chavez JD, Weisbrod CR, Eng JK, Singh PK, Manoil C, Bruce JE. Dynamic Proteome Response of Pseudomonas aeruginosa to Tobramycin Antibiotic Treatment. Mol Cell Proteomics 2015; 14:2126-37. [PMID: 26018413 DOI: 10.1074/mcp.m115.050161] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Indexed: 11/06/2022] Open
Abstract
Genetically susceptible bacteria become antibiotic tolerant during chronic infections, and the mechanisms responsible are poorly understood. One factor that may contribute to differential sensitivity in vitro and in vivo is differences in the time-dependent tobramycin concentration profile experienced by the bacteria. Here, we examine the proteome response induced by subinhibitory concentrations of tobramycin in Pseudomonas aeruginosa cells grown under planktonic conditions. These efforts revealed increased levels of heat shock proteins and proteases were present at higher dosage treatments (0.5 and 1 μg/ml), while less dramatic at 0.1 μg/ml dosage. In contrast, many metabolic enzymes were significantly induced by lower dosages (0.1 and 0.5 μg/ml) but not at 1 μg/ml dosage. Time course proteome analysis further revealed that the increase of heat shock proteins and proteases was most rapid from 15 min to 60 min, and the increased levels sustained till 6 h (last time point tested). Heat shock protein IbpA exhibited the greatest induction by tobramycin, up to 90-fold. Nevertheless, deletion of ibpA did not enhance sensitivity to tobramycin. It seemed possible that the absence of sensitization could be due to redundant functioning of IbpA with other proteins that protect cells from tobramycin. Indeed, inactivation of two heat shock chaperones/proteases in addition to ibpA in double mutants (ibpA/clpB, ibpA/PA0779 and ibpA/hslV) did increase tobramycin sensitivity. Collectively, these results demonstrate the time- and concentration-dependent nature of the P. aeruginosa proteome response to tobramycin and that proteome modulation and protein redundancy are protective mechanisms to help bacteria resist antibiotic treatments.
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Affiliation(s)
- Xia Wu
- From the ‡Department of Genome Sciences
| | | | | | - Benjamin J Staudinger
- ¶Department of Medicine and Microbiology, University of Washington, Seattle, WA 98195
| | | | | | | | - Pradeep K Singh
- ¶Department of Medicine and Microbiology, University of Washington, Seattle, WA 98195
| | | | - James E Bruce
- From the ‡Department of Genome Sciences, §Department of Chemistry,
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25
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Two mechanisms of killing of Pseudomonas aeruginosa by tobramycin assessed at multiple inocula via mechanism-based modeling. Antimicrob Agents Chemother 2015; 59:2315-27. [PMID: 25645838 DOI: 10.1128/aac.04099-14] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacterial resistance is among the most serious threats to human health globally, and many bacterial isolates have emerged that are resistant to all antibiotics in monotherapy. Aminoglycosides are often used in combination therapies against severe infections by multidrug-resistant bacteria. However, models quantifying different antibacterial effects of aminoglycosides are lacking. While the mode of aminoglycoside action on protein synthesis has often been studied, their disruptive action on the outer membrane of Gram-negative bacteria remains poorly characterized. Here, we developed a novel quantitative model for these two mechanisms of aminoglycoside action, phenotypic tolerance at high bacterial densities, and adaptive bacterial resistance in response to an aminoglycoside (tobramycin) against three Pseudomonas aeruginosa strains. At low-intermediate tobramycin concentrations (<4 mg/liter), bacterial killing due to the effect on protein synthesis was most important, whereas disruption of the outer membrane was the predominant killing mechanism at higher tobramycin concentrations (≥8 mg/liter). The extent of killing was comparable across all inocula; however, the rate of bacterial killing and growth was substantially lower at the 10(8.9) CFU/ml inoculum than that at the lower inocula. At 1 to 4 mg/liter tobramycin for strain PAO1-RH, there was a 0.5- to 6-h lag time of killing that was modeled via the time to synthesize hypothetical lethal protein(s). Disruption of the outer bacterial membrane by tobramycin may be critical to enhance the target site penetration of antibiotics used in synergistic combinations with aminoglycosides and thereby combat multidrug-resistant bacteria. The two mechanisms of aminoglycoside action and the new quantitative model hold great promise to rationally design novel, synergistic aminoglycoside combination dosage regimens.
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Shaaban HA, Sadek Z, Edris AE, Saad-Hussein A. Analysis and antibacterial activity of Nigella sativa essential oil formulated in microemulsion system. J Oleo Sci 2015; 64:223-32. [PMID: 25748382 DOI: 10.5650/jos.ess14177] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The Essential oil (EO) of Nigella sativa (black cumin) was extracted from the crude oil and the volatile constituents were characterized using gas chromatographic analysis. The EO was formulated in water-based microemulsion system and its antibacterial activity against six pathogenic bacteria was evaluated using the agar well diffusion method. This activity was compared with two other well known biologically active natural and synthetic antimicrobials namely eugenol and Ceftriaxone(®). Results showed that N. sativa EO microemulsion was highly effective against S. aureus, B. cereus and S. typhimurium even at the lowest tested concentration of that EO in the microemulsion (100.0 μg/well). Interestingly, the EO microemulsion showed higher antibacterial activity than Ceftriaxone solution against S. typhimurium at 400.0 μg/well and almost comparable activity against E. coli at 500.0 μg/well. No activity was detected for the EO microemulsion against L. monocytogenes and P. aeruginosa. Eugenol which was also formulated in microemulsion was less effective than N. sativa EO microemulsion except against P. aeruginosa. The synthetic antibiotic (Ceftriaxone) was effective against most of the six tested bacterial strains. This work is the first report revealing the formulation of N. sativa EO in microemulsion system and investigating its antibacterial activity. The results may offer potential application of that water-based microemulsion in controlling the prevalence of some pathogenic bacteria.
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Affiliation(s)
- Hamdy A Shaaban
- Aroma & Flavor Chemistry Department, National Research Center
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Zavascki AP, Bulitta JB, Landersdorfer CB. Combination therapy for carbapenem-resistant Gram-negative bacteria. Expert Rev Anti Infect Ther 2013; 11:1333-53. [PMID: 24191943 DOI: 10.1586/14787210.2013.845523] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The emergence of resistant to carbapenems Gram-negative bacteria (CR GNB) has severely challenged antimicrobial therapy. Many CR GNB isolates are only susceptible to polymyxins; however, therapy with polymyxins and other potentially active antibiotics presents some drawbacks, which have discouraged their use in monotherapy. In this context, along with strong pre-clinical evidence of benefit in combining antimicrobials against CR GNB, the clinical use of combination therapy has been raised as an interesting strategy to overcome these potential limitations of a single agent. Polymyxins, tigecycline and even carbapenems are usually the cornerstone agents in combination schemes. Optimization of the probability to attain the pharmacokinetic/pharmacodynamic targets by both cornerstone drug and adjuvant drug is of paramount importance to achieve better clinical and microbiological outcomes. Clinical evidence of the major drugs utilized in combination schemes and how they should be prescribed considering pharmacokinetic/pharmacodynamic characteristics against CR GNB will be reviewed in this article.
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Affiliation(s)
- Alexandre P Zavascki
- Infectious Diseases Service, Hospital de Clínicas de Porto Alegre, 2350 Ramiro Barcelos St, Porto Alegre, 90.035-903, Brazil
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Tseng BS, Zhang W, Harrison JJ, Quach TP, Song JL, Penterman J, Singh PK, Chopp DL, Packman AI, Parsek MR. The extracellular matrix protects Pseudomonas aeruginosa biofilms by limiting the penetration of tobramycin. Environ Microbiol 2013; 15:2865-78. [PMID: 23751003 DOI: 10.1111/1462-2920.12155] [Citation(s) in RCA: 216] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Revised: 05/03/2013] [Accepted: 05/07/2013] [Indexed: 01/20/2023]
Abstract
Biofilm cells are less susceptible to antimicrobials than their planktonic counterparts. While this phenomenon is multifactorial, the ability of the matrix to reduce antibiotic penetration into the biofilm is thought to be of limited importance studies suggest that antibiotics move fairly rapidly through biofilms. In this study, we monitored the transport of two clinically relevant antibiotics, tobramycin and ciprofloxacin, into non-mucoid Pseudomonas aeruginosa biofilms. To our surprise, we found that the positively charged antibiotic tobramycin is sequestered to the biofilm periphery, while the neutral antibiotic ciprofloxacin readily penetrated. We provide evidence that tobramycin in the biofilm periphery both stimulated a localized stress response and killed bacteria in these regions but not in the underlying biofilm. Although it is unclear which matrix component binds tobramycin, its penetration was increased by the addition of cations in a dose-dependent manner, which led to increased biofilm death. These data suggest that ionic interactions of tobramycin with the biofilm matrix limit its penetration. We propose that tobramycin sequestration at the biofilm periphery is an important mechanism in protecting metabolically active cells that lie just below the zone of sequestration.
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Affiliation(s)
- Boo Shan Tseng
- Department of Microbiology, University of Washington, Seattle, WA, USA
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Hosseinidoust Z, Tufenkji N, van de Ven TGM. Predation in homogeneous and heterogeneous phage environments affects virulence determinants of Pseudomonas aeruginosa. Appl Environ Microbiol 2013; 79:2862-71. [PMID: 23435883 PMCID: PMC3623153 DOI: 10.1128/aem.03817-12] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Accepted: 02/14/2013] [Indexed: 01/21/2023] Open
Abstract
The rise of bacterial variants in the presence of lytic phages has been one of the basic grounds for evolution studies. However, there are incongruent results among different studies investigating the effect of phage resistance acquisition on bacterial fitness and virulence. We used experimental evolution to generate three classes of Pseudomonas aeruginosa variants under selective pressure from two different homogeneous phage environments and one heterogeneous phage environment. The fitness and virulence determinants of the variants, such as growth, motility, biofilm formation, resistance to oxidative stress, and the production of siderophores and chromophores, changed significantly compared to the control. Variants with similar colony morphology that were developed through different phage treatments have different phenotypic traits. Also, mRNA transcription for genes associated with certain phenotypic traits changed significantly; however, sequencing did not reveal any point mutations in selected gene loci. Furthermore, the appearance of small colony variants and melanogenic variants and the increase in pyocyanin and pyoverdin production for some variants are believed to affect the virulence of the population. The knowledge gained from this study will fundamentally contribute to our understanding of the evolutionary dynamics of bacteria under phage selective pressure which is crucial to the efficient utilization of bacteriophages in medical contexts.
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Affiliation(s)
| | - Nathalie Tufenkji
- Department of Chemical Engineering, McGill University, Montreal, Quebec, Canada
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Teigen MMB, Duffull S, Dang L, Johnson DW. Dosing of Gentamicin in Patients With End-Stage Renal Disease Receiving Hemodialysis. J Clin Pharmacol 2013; 46:1259-67. [PMID: 17050791 DOI: 10.1177/0091270006292987] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The aim of this study was to evaluate dosing schedules of gentamicin in patients with end-stage renal disease and receiving hemodialysis. Forty-six patients were recruited who received gentamicin while on hemodialysis. Each patient provided approximately 4 blood samples at various times before and after dialysis for analysis of plasma gentamicin concentrations. A population pharmacokinetic model was constructed using NONMEM (version 5). The clearance of gentamicin during dialysis was 4.69 L/h and between dialysis was 0.453 L/h. The clearance between dialysis was best described by residual creatinine clearance (as calculated using the Cockcroft and Gault equation), which probably reflects both lean mass and residual clearance mechanisms. Simulation from the final population model showed that predialysis dosing has a higher probability of achieving target maximum concentration (Cmax) concentrations (> 8 mg/L) within acceptable exposure limits (area under the concentration-time curve [AUC] values > 70 and < 120 mg x h/L per 24 hours) than postdialysis dosing.
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Adaptive and mutational resistance: role of porins and efflux pumps in drug resistance. Clin Microbiol Rev 2013; 25:661-81. [PMID: 23034325 DOI: 10.1128/cmr.00043-12] [Citation(s) in RCA: 519] [Impact Index Per Article: 47.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The substantial use of antibiotics in the clinic, combined with a dearth of new antibiotic classes, has led to a gradual increase in the resistance of bacterial pathogens to these compounds. Among the various mechanisms by which bacteria endure the action of antibiotics, those affecting influx and efflux are of particular importance, as they limit the interaction of the drug with its intracellular targets and, consequently, its deleterious effects on the cell. This review evaluates the impact of porins and efflux pumps on two major types of resistance, namely, mutational and adaptive types of resistance, both of which are regarded as key phenomena in the global rise of antibiotic resistance among pathogenic microorganisms. In particular, we explain how adaptive and mutational events can dramatically influence the outcome of antibiotic therapy by altering the mechanisms of influx and efflux of antibiotics. The identification of porins and pumps as major resistance markers has opened new possibilities for the development of novel therapeutic strategies directed specifically against these mechanisms.
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Pagkalis S, Mantadakis E, Mavros MN, Ammari C, Falagas ME. Pharmacological Considerations for the Proper Clinical Use of Aminoglycosides. Drugs 2011; 71:2277-94. [DOI: 10.2165/11597020-000000000-00000] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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Phenotypes of non-attached Pseudomonas aeruginosa aggregates resemble surface attached biofilm. PLoS One 2011; 6:e27943. [PMID: 22132176 PMCID: PMC3221681 DOI: 10.1371/journal.pone.0027943] [Citation(s) in RCA: 188] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2011] [Accepted: 10/28/2011] [Indexed: 01/22/2023] Open
Abstract
For a chronic infection to be established, bacteria must be able to cope with hostile conditions such as low iron levels, oxidative stress, and clearance by the host defense, as well as antibiotic treatment. It is generally accepted that biofilm formation facilitates tolerance to these adverse conditions. However, microscopic investigations of samples isolated from sites of chronic infections seem to suggest that some bacteria do not need to be attached to surfaces in order to establish chronic infections. In this study we employed scanning electron microscopy, confocal laser scanning microscopy, RT-PCR as well as traditional culturing techniques to study the properties of Pseudomonas aeruginosa aggregates. We found that non-attached aggregates from stationary-phase cultures have comparable growth rates to surface attached biofilms. The growth rate estimations indicated that, independently of age, both aggregates and flow-cell biofilm had the same slow growth rate as a stationary phase shaking cultures. Internal structures of the aggregates matrix components and their capacity to survive otherwise lethal treatments with antibiotics (referred to as tolerance) and resistance to phagocytes were also found to be strikingly similar to flow-cell biofilms. Our data indicate that the tolerance of both biofilms and non-attached aggregates towards antibiotics is reversible by physical disruption. We provide evidence that the antibiotic tolerance is likely to be dependent on both the physiological states of the aggregates and particular matrix components. Bacterial surface-attachment and subsequent biofilm formation are considered hallmarks of the capacity of microbes to cause persistent infections. We have observed non-attached aggregates in the lungs of cystic fibrosis patients; otitis media; soft tissue fillers and non-healing wounds, and we propose that aggregated cells exhibit enhanced survival in the hostile host environment, compared with non-aggregated bacterial populations.
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Al-Malky G, Suri R, Dawson SJ, Sirimanna T, Kemp D. Aminoglycoside antibiotics cochleotoxicity in paediatric cystic fibrosis (CF) patients: A study using extended high-frequency audiometry and distortion product otoacoustic emissions. Int J Audiol 2011; 50:112-22. [PMID: 21265638 DOI: 10.3109/14992027.2010.524253] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
UNLABELLED Despite known ototoxic effects of aminoglycoside (AG) antibiotics, audiological assessment is not routinely undertaken in UK CF patients. Consequently, the incidence of hearing loss is not well established. OBJECTIVE To document the incidence of hearing loss in cystic fibrosis (CF) children. DESIGN Hearing function of 45 children from Great Ormond Street Hospital was assessed using pure-tone audiometry up to 20kHz and DPOAEs up to 8kHz. STUDY SAMPLE 39/45 of participants had received intravenous (IV) AGs, 23 of which received repeated IV AGs every 3 months. RESULTS In this high exposure group, 8 (21%) had clear signs of ototoxicity; average 8-20kHz thresholds were elevated by ∼50dB and DPOAE amplitudes were >10dB lower at f2 3.2-6.3 kHz. The remaining 31/39 (79%) of AG exposed patients had normal, even exceptionally good hearing. The 21% incidence of ototoxicity we observed is substantial and higher than previously reported. However, our finding of normal hearing in children with equal AG exposure strongly suggests that other unknown factors, possibly genetic susceptibility, influence this outcome. CONCLUSIONS We recommend comparable auditory testing in all CF patients with high AG exposures. Genetic analysis may help explain the dichotomy in response to AGs found.
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Adaptive resistance to cationic compounds in Pseudomonas aeruginosa. Int J Antimicrob Agents 2011; 37:187-93. [PMID: 21295448 DOI: 10.1016/j.ijantimicag.2010.11.019] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2010] [Accepted: 11/11/2010] [Indexed: 11/20/2022]
Abstract
Adaptive resistance is an autoregulated phenomenon characterised by induction of resistance in the presence of drug and reversal to the sensitive phenotype in its absence. This type of resistance is well documented for polycationic antibiotics, including aminoglycosides and polymyxins, in Pseudomonas aeruginosa and other aerobic Gram-negative bacilli. It is not caused by selection of resistant mutants but rather by phenotypic alterations in order to survive the lethal drug effect. Adaptive resistance to aminoglycosides is mainly mediated by the MexXY-OprM efflux pump that is rapidly upregulated in bacteria surviving the first exposure to aminoglycosides and is downregulated when bacteria are no longer in contact with the drug. A two-component regulatory system designated ParR-ParS plays a major role in adaptive resistance induced by cationic peptides. In the presence of cationic peptides, ParR-ParS activates the lipopolysaccharide modification operon (arnBCADTEF) leading to increased resistance in polymyxins and aminoglycosides. The bactericidal kinetics related to adaptive resistance have important clinical implications and provide a rationale for administering cationic antibiotics in larger initial and longer interval bolus dosing. A better understanding of this phenomenon and the molecular mechanisms responsible will be essential not only for optimum use of cationic antibiotics but also for developing new agents with ability to counteract the detrimental effects of adaptive resistance and thus enhance the therapeutic efficacy of polycationic compounds.
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Fernández L, Breidenstein EBM, Hancock REW. Creeping baselines and adaptive resistance to antibiotics. Drug Resist Updat 2011; 14:1-21. [PMID: 21288762 DOI: 10.1016/j.drup.2011.01.001] [Citation(s) in RCA: 132] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Revised: 01/05/2011] [Accepted: 01/05/2011] [Indexed: 01/22/2023]
Abstract
The introduction of antimicrobial drugs in medicine gave hope for a future in which all infectious diseases could be controlled. Decades later it appears certain this will not be the case, because antibiotic resistance is growing relentlessly. Bacteria possess an extraordinary ability to adapt to environmental challenges like antimicrobials by both genetic and phenotypic means, which contributes to their evolutionary success. It is becoming increasingly appreciated that adaptation is a major mechanism behind the acquisition and evolution of antibiotic resistance. Adaptive resistance is a specific class of non-mutational resistance that is characterized by its transient nature. It occurs in response to certain environmental conditions or due to epigenetic phenomena like persistence. We propose that this type of resistance could be the key to understanding the failure of some antibiotic therapy programs, although adaptive resistance mechanisms are still somewhat unexplored. Similarly, hard wiring of some of the changes involved in adaptive resistance might explain the phenomenon of "baseline creep" whereby the average minimal inhibitory concentration (MIC) of a given medically important bacterial species increases steadily but inexorably over time, making the likelihood of breakthrough resistance greater. This review summarizes the available information on adaptive resistance.
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Affiliation(s)
- Lucía Fernández
- Centre for Microbial Diseases and Immunity Research, Department of Microbiology and Immunology, University of British Columbia, Vancouver, Canada
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Babić F, Venturi V, Maravić-Vlahovicek G. Tobramycin at subinhibitory concentration inhibits the RhlI/R quorum sensing system in a Pseudomonas aeruginosa environmental isolate. BMC Infect Dis 2010; 10:148. [PMID: 20525206 PMCID: PMC2898818 DOI: 10.1186/1471-2334-10-148] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2009] [Accepted: 06/02/2010] [Indexed: 12/22/2022] Open
Abstract
Background Antibiotics are not only small molecules with therapeutic activity in killing or inhibiting microbial growth, but can also act as signaling molecules affecting gene expression in bacterial communities. A few studies have demonstrated the effect of tobramycin as a signal molecule on gene expression at the transcriptional level and its effect on bacterial physiology and virulence. These have shown that subinhibitory concentrations (SICs) of tobramycin induce biofilm formation and enhance the capabilities of P. aeruginosa to colonize specific environments. Methods Environmental P. aeruginosa strain PUPa3 was grown in the presence of different concentrations of tobramycin and it was determined at which highest concentration SIC, growth, total protein levels and translation efficiency were not affected. At SIC it was then established if phenotypes related to cell-cell signaling known as quorum sensing were altered. Results In this study it was determined whether tobramycin sensing/response at SICs was affecting the two independent AHL QS systems in an environmental P. aeruginosa strain. It is reasonable to assume that P. aeruginosa encounters tobramycin in nature since it is produced by niche mate Streptomyces tenebrarius. It was established that SICs of tobramycin inhibited the RhlI/R system by reducing levels of C4-HSL production. This effect was not due to a decrease of rhlI transcription and required tobramycin-ribosome interaction. Conclusions Tobramycin signaling in P. aeruginosa occurs and different strains can have a different response. Understanding the tobramycin response by an environmental P. aeruginosa will highlight possible inter-species signalling taking place in nature and can possible also have important implications in the mode of utilization for human use of this very important antibiotic.
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Affiliation(s)
- Fedora Babić
- Department of Biochemistry and Molecular Biology, University of Zagreb, Croatia
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38
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Aminoglycoside therapy against Pseudomonas aeruginosa in cystic fibrosis: A review. J Cyst Fibros 2009; 8:361-9. [DOI: 10.1016/j.jcf.2009.08.004] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Revised: 07/30/2009] [Accepted: 08/10/2009] [Indexed: 11/23/2022]
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39
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O’Shea S, Duffull S, Johnson DW. Aminoglycosides in Hemodialysis Patients: Is the Current Practice of Post Dialysis Dosing Appropriate? Semin Dial 2009; 22:225-30. [DOI: 10.1111/j.1525-139x.2008.00554.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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40
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Beaulac C, Sachetelli S, Lagace J. In Vitro Bactericidal Evaluation of a Low Phase Transition Temperature Liposomal Tobramycin Formulation as a Dry Powder Preparation Against Gram Negative and Gram Positive Bacteria. J Liposome Res 2008. [DOI: 10.3109/08982109909018652] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Wassil SK, Fox KM, White JW. Once daily dosing of aminoglycosides in pediatric cystic fibrosis patients: a review of the literature. J Pediatr Pharmacol Ther 2008; 13:68-75. [PMID: 23055867 DOI: 10.5863/1551-6776-13.2.68] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Patients with cystic fibrosis receive many courses of antibiotic therapy throughout their lifetime. Dosing aminoglycosides once daily has become common practice in many of these individuals. Due to ease of home administration, decreased nursing time, and improved quality of life, this regimen is being increasingly explored in the cystic fibrosis population. Because patients with cystic fibrosis have increased aminoglycoside clearance, once daily dosing may result in a prolonged time during the dosing interval when concentrations of the drug may be undetectable. This makes the use of once daily dosing of these antibiotics in patients with cystic fibrosis controversial. Although aminoglycosides exhibit a post antibiotic effect, the duration of this effect is unknown in humans; therefore, the development of resistance to the aminoglycoside is a concern. This manuscript will review the organisms most commonly associated with a pulmonary exacerbation of cystic fibrosis, the properties of the aminoglycoside that make once daily dosing feasible, the concept of once daily dosing in those with cystic fibrosis and the current literature regarding efficacy, monitoring, toxicity and concerns of resistance with once daily dosing in this population.
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Affiliation(s)
- Sarah K Wassil
- Department of Pharmacy, Baptist Wolfson Children's Hospital, Jacksonville, Florida
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Abstract
In summary, there is a significant interplay between the pulmonary manifestations and nutritional status of CF patients. The advances in CF clinical care in the past 2 decades are mainly attributed to anti-infective therapy as well as aggressive nutritional management. Currently, there are multiple therapeutic agents that are in clinical trial that target either the underlying CFTR defect or the downstream effects of CFTR. The broad spectrum of therapeutic agents being studied as well as the advances in therapies that target the underlying CFTR defect are exciting, making it likely that at least one of the treatments will make a major difference in how we will treat CF in the future.
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Affiliation(s)
- Reshma Amin
- Division of Respiratory Medicine, Department of Pediatrics, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, ON, M5G 1X8, Canada
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Brazas MD, Breidenstein EBM, Overhage J, Hancock REW. Role of lon, an ATP-dependent protease homolog, in resistance of Pseudomonas aeruginosa to ciprofloxacin. Antimicrob Agents Chemother 2007; 51:4276-83. [PMID: 17893152 PMCID: PMC2167996 DOI: 10.1128/aac.00830-07] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
With few novel antimicrobials in the pharmaceutical pipeline, resistance to the current selection of antibiotics represents a significant therapeutic challenge. Microbial persistence in subinhibitory antibiotic environments has been proposed to contribute to the development of resistance. Pseudomonas aeruginosa cultures pretreated with subinhibitory concentrations of ciprofloxacin were found to exhibit an adaptive resistance phenotype when cultures were subsequently exposed to suprainhibitory ciprofloxacin concentrations. Microarray experiments revealed candidate genes involved in such adaptive resistance. Screening of 10,000 Tn5-luxCDABE mutants identified several mutants with increased or decreased ciprofloxacin susceptibilities, including mutants in PA1803, a close homolog of the ATP-dependent lon protease, which were found to exhibit > or = 4-fold-increased susceptibilities to ciprofloxacin and other fluoroquinolones, but not to gentamicin or imipenem, as well as a characteristic elongated morphology. Complementation of the lon mutant restored wild-type antibiotic susceptibility and cell morphology. Expression of the lon mutant, as monitored through a luciferase reporter fusion, was found to increase over time in the presence of subinhibitory ciprofloxacin concentrations. The data are consistent with the hypothesis that the induction of Lon by ciprofloxacin is involved in adaptive resistance.
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Affiliation(s)
- Michelle D Brazas
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
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Abstract
PURPOSE OF REVIEW Over the past four decades, outcomes for patients with cystic fibrosis have improved dramatically. Major contributors to this improvement are a better understanding of disease pathogenesis and the systematic conduct of clinical trials evaluating new therapies designed to address these defects. This review describes recent developments in cystic fibrosis pulmonary therapies intended to treat various facets of the disease, including several treatments currently in development. RECENT FINDINGS The mainstays of therapy for cystic fibrosis, such as nutritional support and mechanical mucus clearance, are now supplemented with aggressive antibiotic regimens intended to suppress or eradicate bacterial colonization, anti-inflammatory agents, and new approaches that improve mucociliary clearance. Therapies in development address the underlying ion transport defect found in cystic fibrosis airways and also include small-molecule agents that restore function to the mutant cystic fibrosis transmembrane conductance regulator. SUMMARY Recent advances in therapies for cystic fibrosis offer the promise of improved outcomes and longer lives for patients with cystic fibrosis.
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Affiliation(s)
- Steven M Rowe
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
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Maciá MD, Borrell N, Segura M, Gómez C, Pérez JL, Oliver A. Efficacy and potential for resistance selection of antipseudomonal treatments in a mouse model of lung infection by hypermutable Pseudomonas aeruginosa. Antimicrob Agents Chemother 2006; 50:975-83. [PMID: 16495260 PMCID: PMC1426455 DOI: 10.1128/aac.50.3.975-983.2006] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Hypermutable Pseudomonas aeruginosa strains are found with high frequency in the lungs of patients with chronic infections and are associated with high antibiotic resistance rates. The in vivo consequences of hypermutation for treatment in a mouse model of lung infection using strain PAO1 and its hypermutable derivative PAOdeltamutS are investigated. Groups of 30 mice were treated for 3 days with humanized regimens of ciprofloxacin (CIP), tobramycin (TOB), CIP plus TOB, or placebo, and mortality, total lung bacterial load, and 4x- and 16x-MIC mutants were recorded. The rates of mutation and the initial in vivo frequencies of mutants (at the onset of treatment) were also estimated and the in vitro- and in vivo-selected mutants characterized. Since both strains had identical MICs, the same pharmacokinetic/pharmacodynamic (PK/PD) parameters were obtained: area under the 24-h concentration-time curve (fAUC)/MIC = 385 for CIP and maximum concentration of drug in serum (fC(max))/MIC = 19 for TOB. Despite adequate PK/PD parameters, persistence of high bacterial numbers and amplification (50,000-fold) of resistant mutants (MexCD-OprJ hyperexpression) were documented with CIP treatment for PAOdeltamutS, in contrast to complete resistance suppression for PAO1 (P < 0.01), showing that conventional PK/PD parameters may not be applicable to infections by hypermutable strains. On the other hand, the efficacy of TOB monotherapy in terms of mortality reduction and bacterial load was very low regardless of the strain but not due to resistance development, since mutants were not selected for PAO1 and were only modestly amplified for PAOdeltamutS. Finally, the CIP-plus-TOB combination was synergistic, further reducing mortality and bacterial load and completely preventing resistance even for PAOdeltamutS (P < 0.01 compared to monotherapy), showing that it is possible to suppress resistance selection in infections by hypermutable P. aeruginosa using appropriate combined regimens.
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Affiliation(s)
- M D Maciá
- Servicio de Microbiología, Hospital Son Dureta, C. Andrea Doria No. 55, 07014 Palma de Mallorca, Spain
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Abstract
1. The role of the clinical pharmacologist is to promote the rational, safe and effective use of medicines. This revolves around the notion of variability, between and within patients and between and within drugs, in terms of both pharmacokinetics and pharmacodynamics. Ideal therapeutics involves tailoring the drug and its dosing to the individual patient, taking into account this variability. 2. In the 25 years of my membership of the Australasian Society of Clinical and Experimental Pharmacologists and Toxicologists, three themes have dominated my research: (i) drugs and breast feeding; (ii) aminoglycoside dosing; and (iii) pharmacogenetics. In all these, the research has been orientated towards identifying factors involved in variability and working towards dose individualization based on the understanding of these factors. 3. Our model for predicting drug concentrations in milk has assisted not only in estimating the safety of drug ingestion via breast milk, but also in the understanding of the processes involved in drug transfer. 4. The aminoglycoside studies have assisted in the understanding of the basis behind extended interval dosing, leading to a model for dose prediction that is widely used, especially in Australasia. 5. Pharmacogenetics is a field widely acclaimed as having a huge future in terms of individualization of drug therapy. Our early studies in this area lend only cautious support to this optimism.
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Affiliation(s)
- E J Begg
- Department of Medicine, Christchurch School of Medicine, Christchurch, New Zealand.
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Hoffman LR, D'Argenio DA, MacCoss MJ, Zhang Z, Jones RA, Miller SI. Aminoglycoside antibiotics induce bacterial biofilm formation. Nature 2005; 436:1171-5. [PMID: 16121184 DOI: 10.1038/nature03912] [Citation(s) in RCA: 834] [Impact Index Per Article: 43.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2005] [Accepted: 06/09/2005] [Indexed: 12/24/2022]
Abstract
Biofilms are adherent aggregates of bacterial cells that form on biotic and abiotic surfaces, including human tissues. Biofilms resist antibiotic treatment and contribute to bacterial persistence in chronic infections. Hence, the elucidation of the mechanisms by which biofilms are formed may assist in the treatment of chronic infections, such as Pseudomonas aeruginosa in the airways of patients with cystic fibrosis. Here we show that subinhibitory concentrations of aminoglycoside antibiotics induce biofilm formation in P. aeruginosa and Escherichia coli. In P. aeruginosa, a gene, which we designated aminoglycoside response regulator (arr), was essential for this induction and contributed to biofilm-specific aminoglycoside resistance. The arr gene is predicted to encode an inner-membrane phosphodiesterase whose substrate is cyclic di-guanosine monophosphate (c-di-GMP)-a bacterial second messenger that regulates cell surface adhesiveness. We found that membranes from arr mutants had diminished c-di-GMP phosphodiesterase activity, and P. aeruginosa cells with a mutation changing a predicted catalytic residue of Arr were defective in their biofilm response to tobramycin. Furthermore, tobramycin-inducible biofilm formation was inhibited by exogenous GTP, which is known to inhibit c-di-GMP phosphodiesterase activity. Our results demonstrate that biofilm formation can be a specific, defensive reaction to the presence of antibiotics, and indicate that the molecular basis of this response includes alterations in the level of c-di-GMP.
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Affiliation(s)
- Lucas R Hoffman
- Department of Pediatrics, University of Washington, Seattle, Washington 98195, USA
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Morosini MI, García-Castillo M, Loza E, Pérez-Vázquez M, Baquero F, Cantón R. Breakpoints for predicting Pseudomonas aeruginosa susceptibility to inhaled tobramycin in cystic fibrosis patients: use of high-range Etest strips. J Clin Microbiol 2005; 43:4480-5. [PMID: 16145095 PMCID: PMC1234086 DOI: 10.1128/jcm.43.9.4480-4485.2005] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2005] [Revised: 05/20/2005] [Accepted: 06/14/2005] [Indexed: 01/05/2023] Open
Abstract
Inhaled administration of tobramycin assures high concentrations in cystic fibrotic lungs, improving the therapeutic ratio over that of parenteral tobramycin levels, particularly against Pseudomonas aeruginosa. Conventional Clinical and Laboratory Standards Institute (CLSI; formerly National Committee for Clinical Laboratory Standards) breakpoints only consider parenteral levels and do not take into account these high antimicrobial concentrations. The Spanish Antibiogram Committee (The MENSURA Group) has tentatively defined specific breakpoint values for inhaled tobramycin when testing P. aeruginosa isolates from cystic fibrosis (CF) patients (susceptible, < or =64 microg/ml; resistant, > or =128 microg/ml). The antimicrobial susceptibilities of 206 prospectively collected CF P. aeruginosa isolates were determined by the reference agar dilution method. For tobramycin, the performance of high range tobramycin Etest strips (AB Biodisk, Solna, Sweden) and conventional tobramycin disks were assessed with the same collection. Applying MENSURA proposed breakpoints, 95.1% of the strains were categorized as susceptible to tobramycin, either using agar dilution or Etest high-range strips (99% categorical agreement between both methods). With CLSI breakpoints, susceptibility rates decreased to 79.1 and 81.1% for agar dilution and Etest strips, respectively (83.5% categorical agreement). Minor, major, and very major errors for Etest strips (CLSI criteria) were 13.6, 1.2, and 14.8%, respectively. Upon applying the new proposed criteria for inhaled tobramycin, only one major and one very major error were observed with Etest strips. Whenever inhaled tobramycin is considered for therapy, we suggest that P. aeruginosa strains from CF patients categorized as intermediate or resistant to tobramycin according to the CLSI criteria should be retested with high-range Etest strips and recategorized using MENSURA interpretive criteria. CLSI breakpoints should still be followed when intravenous tobramycin is used in CF patients, particularly during the course of exacerbations.
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Affiliation(s)
- María I Morosini
- Servicio de Microbiología, Hospital Universitario Ramón y Cajal, Madrid, Spain
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Affiliation(s)
- Keith Poole
- Department of Microbiology & Immunology, Rm. 737 Botterell Hall, Queen's University, Kingston, ON K7L 3N6, Canada.
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