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Blehm CJ, Monteiro MSG, Bessa MC, Leyser M, Dias AS, Sumienski J, Gallo SW, da Silva AB, Barros A, Marco R, Preve CP, Ferreira CAS, Ramos F, de Oliveira SD. Copper-coated hospital surfaces: reduction of total bacterial loads and resistant Acinetobacter spp. AMB Express 2022; 12:146. [DOI: 10.1186/s13568-022-01491-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Accepted: 11/11/2022] [Indexed: 11/24/2022] Open
Abstract
AbstractHealthcare-associated infections (HAIs) represent a global challenge and an even more staggering concern when related to microorganisms capable of resisting and surviving for long periods in the environment, such as Acinetobacter spp. Strategies that allow a reduction of pathogens from hospital environments represent an additional barrier in infection control protocols, minimizing transmission to hospitalized patients. Considering the antimicrobial properties of copper, here, the bacterial load and the presence of Acinetobacter spp. were monitored on high handling surfaces covered by 99.9% copper films on intensive and non-intensive care unit bedrooms in a tertiary care hospital. Firstly, copper-coated films were able to inhibit the adhesion and biofilm formation of A. baumannii strains in in vitro assays. On the other hand, Acinetobacter spp. were isolated from both copper-coated and uncoated surfaces in the hospital, although the majority was detected on surfaces without copper. All carbapenem-resistant A. baumannii isolates identified harbored the blaoxa-23 gene, while the A. nosocomialis isolates were susceptible to most antimicrobials tested. All isolates were susceptible to polymyxin B. Regarding the total aerobic bacteria, surfaces with copper-coated films presented lower total loads than those detected for controls. Copper coating films may be a workable strategy to mitigate HAIs, given their potential in reducing bacterial loads in nosocomial environments, including threatening pathogens like A. baumannii.
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Genetic Diversity of Antimicrobial Resistance and Key Virulence Features in Two Extensively Drug-Resistant Acinetobacter baumannii Isolates. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:ijerph19052870. [PMID: 35270562 PMCID: PMC8910769 DOI: 10.3390/ijerph19052870] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 02/25/2022] [Accepted: 02/27/2022] [Indexed: 01/27/2023]
Abstract
In recent decades, Acinetobacter baumannii emerged as a major infective menace in healthcare settings due to scarce therapeutic options to treat infections. Therefore, undertaking genome comparison analyses of multi-resistant A. baumannii strains could aid the identification of key bacterial determinants to develop innovative anti-virulence approaches. Following genome sequencing, we performed a molecular characterization of key genes and genomic comparison of two A. baumannii strains, #36 and #150, with selected reference genomes. Despite a different antibiotic resistance gene content, the analyzed strains showed a very similar antibiogram profile. Interestingly, the lack of some important virulence determinants (i.e., bap, ata and omp33–36) did not abrogate their adhesive abilities to abiotic and biotic surfaces, as reported before; indeed, strains retained these capacities, although to a different extent, suggesting the presence of distinct vicarious genes. Conversely, secretion systems, lipopolysaccharide (LPS), capsule and iron acquisition systems were highly similar to A. baumannii reference strains. Overall, our analyses increased our knowledge on A. baumannii genomic content and organization as well as the genomic events occurring in nosocomial isolates to better fit into changing healthcare environments.
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Identification of Two Variants of Acinetobacter baumannii Strain ATCC 17978 with Distinct Genotypes and Phenotypes. Infect Immun 2021; 89:e0045421. [PMID: 34460288 DOI: 10.1128/iai.00454-21] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Acinetobacter baumannii is a nosocomial pathogen that exhibits substantial genomic plasticity. Here, the identification of two variants of A. baumannii ATCC 17978 that differ based on the presence of a 44-kb accessory locus, named AbaAL44 (A. baumannii accessory locus 44 kb), is described. Analyses of existing deposited data suggest that both variants are found in published studies of A. baumannii ATCC 17978 and that American Type Culture Collection (ATCC)-derived laboratory stocks comprise a mix of these two variants. Yet, each variant exhibits distinct interactions with the host in vitro and in vivo. Infection with the variant that harbors AbaAL44 (A. baumannii 17978 UN) results in decreased bacterial burdens and increased neutrophilic lung inflammation in a mouse model of pneumonia, and affects the production of interleukin 1 beta (IL-1β) and IL-10 by infected macrophages. AbaAL44 harbors putative pathogenesis genes, including those predicted to encode a type I pilus cluster, a catalase, and a cardiolipin synthase. The accessory catalase increases A. baumannii resistance to oxidative stress and neutrophil-mediated killing in vitro. The accessory cardiolipin synthase plays a dichotomous role by promoting bacterial uptake and increasing IL-1β production by macrophages, but also by enhancing bacterial resistance to cell envelope stress. Collectively, these findings highlight the phenotypic consequences of the genomic dynamism of A. baumannii through the evolution of two variants of a common type strain with distinct infection-related attributes.
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Rakovitsky N, Lellouche J, Ben David D, Frenk S, Elmalih P, Weber G, Kon H, Schwartz D, Wolfhart L, Temkin E, Carmeli Y. Increased Capsule Thickness and Hypermotility Are Traits of Carbapenem-Resistant Acinetobacter baumannii ST3 Strains Causing Fulminant Infection. Open Forum Infect Dis 2021; 8:ofab386. [PMID: 34514017 PMCID: PMC8423469 DOI: 10.1093/ofid/ofab386] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Accepted: 07/18/2021] [Indexed: 12/13/2022] Open
Abstract
Background Acinetobacter baumannii is a successful nosocomial pathogen, causing severe, life-threatening infections in hospitalized patients, including pneumonia and bloodstream infections. The spread of carbapenem-resistant Acinetobacter baumannii (CRAB) strains is a major health threat worldwide. The successful spread of CRAB is mostly due to its highly plastic genome. Although some virulence factors associated with CRAB have been uncovered, many mechanisms contributing to its success are not fully understood. Methods Here we describe strains of CRAB that were isolated from fulminant cases in 2 hospitals in Israel. These isolates show a rare hypermucoid (HM) phenotype and were investigated using phenotypic assays, comparative genomics, and an in vivo Galleria mellonella model. Results The 3 isolates belonged to the ST3 international clonal type and were closely related to each other, as shown by Fourier-transform infrared spectroscopy and phylogenetic analyses. These isolates possessed thickened capsules and a dense filamentous extracellular polysaccharides matrix as shown by transmission electron microscopy (TEM), and overexpressed the capsule polysaccharide synthesis pathway-related wzc gene. Conclusions The HM isolates possessed a unique combination of virulence genes involved in iron metabolism, protein secretion, adherence, and membrane glycosylation. HM strains were more virulent than control strains in 2 G. mellonella infection models. In conclusion, our findings demonstrated several virulence factors, all present in 3 CRAB isolates with rare hypermucoid phenotypes.
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Affiliation(s)
- Nadya Rakovitsky
- National Institute for Antibiotic Resistance and Infection Control, Ministry of Health, Tel-Aviv, Israel
| | - Jonathan Lellouche
- National Institute for Antibiotic Resistance and Infection Control, Ministry of Health, Tel-Aviv, Israel
| | - Debby Ben David
- National Institute for Antibiotic Resistance and Infection Control, Ministry of Health, Tel-Aviv, Israel.,Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel
| | - Sammy Frenk
- National Institute for Antibiotic Resistance and Infection Control, Ministry of Health, Tel-Aviv, Israel
| | - Polet Elmalih
- National Institute for Antibiotic Resistance and Infection Control, Ministry of Health, Tel-Aviv, Israel
| | - Gabriel Weber
- The B. Rappaport Faculty of Medicine, Technion, Israel Institute of Technology, Haifa, Israel.,Infectious Disease and Infection Control Unit, Carmel Medical Center, Haifa, Israel
| | - Hadas Kon
- National Institute for Antibiotic Resistance and Infection Control, Ministry of Health, Tel-Aviv, Israel
| | - David Schwartz
- National Institute for Antibiotic Resistance and Infection Control, Ministry of Health, Tel-Aviv, Israel
| | - Liat Wolfhart
- National Institute for Antibiotic Resistance and Infection Control, Ministry of Health, Tel-Aviv, Israel
| | - Elizabeth Temkin
- National Institute for Antibiotic Resistance and Infection Control, Ministry of Health, Tel-Aviv, Israel
| | - Yehuda Carmeli
- National Institute for Antibiotic Resistance and Infection Control, Ministry of Health, Tel-Aviv, Israel.,Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel
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Acinetobacter baumannii Antibiotic Resistance Mechanisms. Pathogens 2021; 10:pathogens10030373. [PMID: 33808905 PMCID: PMC8003822 DOI: 10.3390/pathogens10030373] [Citation(s) in RCA: 182] [Impact Index Per Article: 60.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2021] [Revised: 03/16/2021] [Accepted: 03/18/2021] [Indexed: 12/11/2022] Open
Abstract
Acinetobacter baumannii is a Gram-negative ESKAPE microorganism that poses a threat to public health by causing severe and invasive (mostly nosocomial) infections linked with high mortality rates. During the last years, this pathogen displayed multidrug resistance (MDR), mainly due to extensive antibiotic abuse and poor stewardship. MDR isolates are associated with medical history of long hospitalization stays, presence of catheters, and mechanical ventilation, while immunocompromised and severely ill hosts predispose to invasive infections. Next-generation sequencing techniques have revolutionized diagnosis of severe A. baumannii infections, contributing to timely diagnosis and personalized therapeutic regimens according to the identification of the respective resistance genes. The aim of this review is to describe in detail all current knowledge on the genetic background of A. baumannii resistance mechanisms in humans as regards beta-lactams (penicillins, cephalosporins, carbapenems, monobactams, and beta-lactamase inhibitors), aminoglycosides, tetracyclines, fluoroquinolones, macrolides, lincosamides, streptogramin antibiotics, polymyxins, and others (amphenicols, oxazolidinones, rifamycins, fosfomycin, diaminopyrimidines, sulfonamides, glycopeptide, and lipopeptide antibiotics). Mechanisms of antimicrobial resistance refer mainly to regulation of antibiotic transportation through bacterial membranes, alteration of the antibiotic target site, and enzymatic modifications resulting in antibiotic neutralization. Virulence factors that may affect antibiotic susceptibility profiles and confer drug resistance are also being discussed. Reports from cases of A. baumannii coinfection with SARS-CoV-2 during the COVID-19 pandemic in terms of resistance profiles and MDR genes have been investigated.
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Ma C, Chen W. Where are we and how far is there to go in the development of an Acinetobacter vaccine? Expert Rev Vaccines 2021; 20:281-295. [PMID: 33554671 DOI: 10.1080/14760584.2021.1887735] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
INTRODUCTION Healthcare-associated infections caused by multidrug-resistant Acinetobacter baumannii are becoming alarming worldwide. However, the pipeline of new antibiotics is very limited. Vaccination is one of the most cost effective and promising strategies to prevent infections and can play an important role in combat multidrug resistance A. baumannii and prevent the development of new drug resistance. AREA COVERED This review gives an overview of the research and development of A. baumannii vaccines during the past five years (2015-2020), discusses the key progresses and current challenges of the field, and speculates on the future of A. baumannii vaccine development. EXPERT OPINION Moderate progresses have been made in the research and development of A. baumannii vaccine in the last five years, in particular in the areas of identification of new protein targets, development of multicomponent vaccines, and use of vaccines and antibodies as adjuncts for antibiotics therapies. However, substantial scientific and logistic challenges, such as selection of lead vaccine candidates and formulation, vaccine clinical trials and targeted population, and financial incentives, remain. Thus, innovative strategies will be needed before an A. baumannii vaccine candidate can be brought into late stage of preclinical development in next five years.
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Affiliation(s)
- Crystal Ma
- Human Health Therapeutics Research Center (HHT), National Research Council Canada, Ottawa, Ontario Canada
| | - Wangxue Chen
- Human Health Therapeutics Research Center (HHT), National Research Council Canada, Ottawa, Ontario Canada.,Department of Biology, Brock University, St. Catharines, Ontario Canada
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Light Modulates Important Pathogenic Determinants and Virulence in ESKAPE Pathogens Acinetobacter baumannii, Pseudomonas aeruginosa, and Staphylococcus aureus. J Bacteriol 2021; 203:JB.00566-20. [PMID: 33288627 DOI: 10.1128/jb.00566-20] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Accepted: 12/03/2020] [Indexed: 02/07/2023] Open
Abstract
Light sensing has been extensively characterized in the human pathogen Acinetobacter baumannii at environmental temperatures. However, the influence of light on the physiology and pathogenicity of human bacterial pathogens at temperatures found in warm-blooded hosts is still poorly understand. In this work, we show that Staphylococcus aureus, Acinetobacter baumannii, and Pseudomonas aeruginosa (ESKAPE) priority pathogens, which have been recognized by the WHO and the CDC as critical, can also sense and respond to light at temperatures found in human hosts. Most interestingly, in these pathogens, light modulates important pathogenicity determinants as well as virulence in an epithelial infection model, which could have implications in human infections. In fact, we found that alpha-toxin-dependent hemolysis, motility, and growth under iron-deprived conditions are modulated by light in S. aureus Light also regulates persistence, metabolism, and the ability to kill competitors in some of these microorganisms. Finally, light exerts a profound effect on the virulence of these pathogens in an epithelial infection model, although the response is not the same in the different species; virulence was enhanced by light in A. baumannii and S. aureus, while in A. nosocomialis and P. aeruginosa it was reduced. Neither the BlsA photoreceptor nor the type VI secretion system (T6SS) is involved in virulence modulation by light in A. baumannii Overall, this fundamental knowledge highlights the potential use of light to control pathogen virulence, either directly or by manipulating the light regulatory switch toward the lowest virulence/persistence configuration.IMPORTANCE Pathogenic bacteria are microorganisms capable of producing disease. Dangerous bacterial pathogens, such as Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii, are responsible for serious intrahospital and community infections in humans. Therapeutics is often complicated due to resistance to multiple antibiotics, rendering them ineffective. In this work, we show that these pathogens sense natural light and respond to it by modulating aspects related to their ability to cause disease; in the presence of light, some of them become more aggressive, while others show an opposite response. Overall, we provide new understanding on the behavior of these pathogens, which could contribute to the control of infections caused by them. Since the response is distributed in diverse pathogens, this notion could prove a general concept.
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Mea HJ, Yong PVC, Wong EH. An overview of Acinetobacter baumannii pathogenesis: Motility, adherence and biofilm formation. Microbiol Res 2021; 247:126722. [PMID: 33618061 DOI: 10.1016/j.micres.2021.126722] [Citation(s) in RCA: 53] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Revised: 01/29/2021] [Accepted: 02/01/2021] [Indexed: 12/13/2022]
Abstract
The Gram-negative opportunistic pathogen Acinetobacter baumannii has gain notoriety in recent decades, primarily due to its propensity to cause nosocomial infections in critically ill patients. Its global spread, multi-drug resistance features and plethora of virulence factors make it a serious threat to public health worldwide. Though much effort has been expended in uncovering its successes, it continues to confound researchers due to its highly adaptive nature, mutating to meet the needs of a given environment. Its persistence in the clinical setting allows it to be in close proximity to a potential host, where contact can be made facilitating infection and colonization. In this article, we aim to provide a current overview of the bacterial virulence factors, specifically focusing on factors involved in the initial stages of infection, highlighting the role of adaptation facilitated by two-component systems and biofilm formation. Finally, the study of host-pathogen interactions using available animal models, their suitability, notable findings and some perspectives moving forward are also discussed.
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Affiliation(s)
- Hing Jian Mea
- School of Biosciences, Faculty of Health and Medical Sciences, Taylor's University Lakeside Campus, 47500, Subang Jaya, Selangor Darul Ehsan, Malaysia
| | - Phelim Voon Chen Yong
- School of Biosciences, Faculty of Health and Medical Sciences, Taylor's University Lakeside Campus, 47500, Subang Jaya, Selangor Darul Ehsan, Malaysia
| | - Eng Hwa Wong
- School of Medicine, Faculty of Health and Medical Sciences, Taylor's University Lakeside Campus, 47500, Subang Jaya, Selangor Darul Ehsan, Malaysia.
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Kulkarni G, Challa J. The first Indian viridescent Acinetobacter lwoffii. Indian J Med Microbiol 2020; 39:130-132. [PMID: 33610246 DOI: 10.1016/j.ijmmb.2020.09.001] [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: 03/28/2020] [Accepted: 09/20/2020] [Indexed: 12/01/2022]
Abstract
Many pathogenic organisms do produce different types of the pigments, helpful in the presumptive laboratory diagnosis of the microorganisms. These pigments are malevolent as well as benevolent to the mankind. Most of the time, the pigmented organisms do display resistance to the many classes of the drugs in vitro and in vivo. Most of Acinetobacter sp are nonpigmented. Few strains produce diffusible brown pigment and rarely produce black and indigo coloured pigments (Liu1 and Nizet, 2009; Nosanchuk and Casadevall, 2003; Moazamian et al., 2018; Saviola, 2018; Saviola, 2014; Kirti et al., 2014; German et al., 2018; Coelho-Souza et al., 2014) [1-8]. This is the first Indian human case report is of "The Viridescent Acinetobacter lwoffii" (dark green pigmented) isolated from the central line blood culture which was susceptible to the many classes of the drugs in vitro and correlated well with in vivo compliance.
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Affiliation(s)
- Grishma Kulkarni
- G-5,a Block, pbr Estates, Padmacolony, Nallakunta Hyderabad India.
| | - Jaswanth Challa
- G-5,a Block, pbr Estates, Padmacolony, Nallakunta Hyderabad India
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10
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Laird TS, Flores N, Leveau JHJ. Bacterial catabolism of indole-3-acetic acid. Appl Microbiol Biotechnol 2020; 104:9535-9550. [PMID: 33037916 DOI: 10.1007/s00253-020-10938-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 09/21/2020] [Accepted: 09/27/2020] [Indexed: 12/18/2022]
Abstract
Indole-3-acetic acid (IAA) is a molecule with the chemical formula C10H9NO2, with a demonstrated presence in various environments and organisms, and with a biological function in several of these organisms, most notably in plants where it acts as a growth hormone. The existence of microorganisms with the ability to catabolize or assimilate IAA has long been recognized. To date, two sets of gene clusters underlying this property in bacteria have been identified and characterized: one (iac) is responsible for the aerobic degradation of IAA into catechol, and another (iaa) for the anaerobic conversion of IAA to 2-aminobenzoyl-CoA. Here, we summarize the literature on the products, reactions, and pathways that these gene clusters encode. We explore two hypotheses about the benefit that iac/iaa gene clusters confer upon their bacterial hosts: (1) exploitation of IAA as a source of carbon, nitrogen, and energy; and (2) interference with IAA-dependent processes and functions in other organisms, including plants. The evidence for both hypotheses will be reviewed for iac/iaa-carrying model strains of Pseudomonas putida, Enterobacter soli, Acinetobacter baumannii, Paraburkholderia phytofirmans, Caballeronia glathei, Aromatoleum evansii, and Aromatoleum aromaticum, more specifically in the context of access to IAA in the environments from which these bacteria were originally isolated, which include not only plants, but also soils and sediment, as well as patients in hospital environments. We end the mini-review with an outlook for iac/iaa-inspired research that addresses current gaps in knowledge, biotechnological applications of iac/iaa-encoded enzymology, and the use of IAA-destroying bacteria to treat pathologies related to IAA excess in plants and humans. KEY POINTS: • The iac/iaa gene clusters encode bacterial catabolism of the plant growth hormone IAA. • Plants are not the only environment where IAA or IAA-degrading bacteria can be found. • The iac/iaa genes allow growth at the expense of IAA; other benefits remain unknown.
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Affiliation(s)
- Tyler S Laird
- Department of Plant Pathology, University of California Davis, Davis, CA, 95616, USA
| | - Neptali Flores
- Department of Plant Pathology, University of California Davis, Davis, CA, 95616, USA
| | - Johan H J Leveau
- Department of Plant Pathology, University of California Davis, Davis, CA, 95616, USA.
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Alzuhairi MA, Abdulmohsen AM, Falih MN, Hanafiah MM. Genomic sequencing analysis of Acinetobacter baumannii strain ABIQM1, isolated from a meningitis patient. GENE REPORTS 2020. [DOI: 10.1016/j.genrep.2020.100631] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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12
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Ramirez MS, Bonomo RA, Tolmasky ME. Carbapenemases: Transforming Acinetobacter baumannii into a Yet More Dangerous Menace. Biomolecules 2020; 10:biom10050720. [PMID: 32384624 PMCID: PMC7277208 DOI: 10.3390/biom10050720] [Citation(s) in RCA: 111] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 04/27/2020] [Accepted: 04/29/2020] [Indexed: 02/07/2023] Open
Abstract
Acinetobacter baumannii is a common cause of serious nosocomial infections. Although community-acquired infections are observed, the vast majority occur in people with preexisting comorbidities. A. baumannii emerged as a problematic pathogen in the 1980s when an increase in virulence, difficulty in treatment due to drug resistance, and opportunities for infection turned it into one of the most important threats to human health. Some of the clinical manifestations of A. baumannii nosocomial infection are pneumonia; bloodstream infections; lower respiratory tract, urinary tract, and wound infections; burn infections; skin and soft tissue infections (including necrotizing fasciitis); meningitis; osteomyelitis; and endocarditis. A. baumannii has an extraordinary genetic plasticity that results in a high capacity to acquire antimicrobial resistance traits. In particular, acquisition of resistance to carbapenems, which are among the antimicrobials of last resort for treatment of multidrug infections, is increasing among A. baumannii strains compounding the problem of nosocomial infections caused by this pathogen. It is not uncommon to find multidrug-resistant (MDR, resistance to at least three classes of antimicrobials), extensively drug-resistant (XDR, MDR plus resistance to carbapenems), and pan-drug-resistant (PDR, XDR plus resistance to polymyxins) nosocomial isolates that are hard to treat with the currently available drugs. In this article we review the acquired resistance to carbapenems by A. baumannii. We describe the enzymes within the OXA, NDM, VIM, IMP, and KPC groups of carbapenemases and the coding genes found in A. baumannii clinical isolates.
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Affiliation(s)
- Maria Soledad Ramirez
- Center for Applied Biotechnology Studies, Department of Biological Science, California State University Fullerton, Fullerton, CA 92831, USA;
| | - Robert A. Bonomo
- Medical Service and GRECC, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, OH 44106, USA;
- Departments of Medicine, Pharmacology, Molecular Biology and Microbiology, Biochemistry, Proteomics and Bioinformatics; Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
- WRU-Cleveland VAMC Center for Antimicrobial Resistance and Epidemiology (Case VA CARES), Cleveland, OH 44106, USA
| | - Marcelo E. Tolmasky
- Center for Applied Biotechnology Studies, Department of Biological Science, California State University Fullerton, Fullerton, CA 92831, USA;
- Correspondence: ; Tel.: +657-278-5263
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The Tip of the VgrG Spike Is Essential to Functional Type VI Secretion System Assembly in Acinetobacter baumannii. mBio 2020; 11:mBio.02761-19. [PMID: 31937641 PMCID: PMC6960284 DOI: 10.1128/mbio.02761-19] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The type VI secretion system (T6SS) is a critical weapon in bacterial warfare between Gram-negative bacteria. Although invaluable for niche establishment, this machine represents an energetic burden to its host bacterium. Acinetobacter baumannii is an opportunistic pathogen that poses a serious threat to public health due to its high rates of multidrug resistance. In some A. baumannii strains, the T6SS is transcriptionally downregulated by large multidrug resistance plasmids. Other strains, such as the clinical isolate AbCAN2, express T6SS-related genes but lack T6SS activity under laboratory conditions, despite not harboring these plasmids. This suggests that alternative mechanisms exist to repress the T6SS. Here, we used a transposon mutagenesis approach in AbCAN2 to identify novel T6SS repressors. Our screen revealed that the T6SS of this strain is inhibited by a homolog of VgrG, an essential structural component of all T6SSs reported to date. We named this protein inhibitory VgrG (VgrGi). Biochemical and in silico analyses demonstrated that the unprecedented inhibitory capability of VgrGi is due to a single amino acid mutation in a widely conserved C-terminal domain of unknown function, DUF2345. We also show that unlike in other bacteria, the C terminus of VgrG is essential for functional T6SS assembly in A. baumannii Our study provides insight into the architectural requirements underlying functional assembly of the T6SS of A. baumannii We propose that T6SS-inactivating point mutations are beneficial to the host bacterium, since they eliminate the energy cost associated with maintaining a functional T6SS, which appears to be unnecessary for A. baumannii virulence.IMPORTANCE Despite the clinical relevance of A. baumannii, little is known about its fundamental biology. Here, we show that a single amino acid mutation in VgrG, a critical T6SS structural protein, abrogates T6SS function. Given that this mutation was found in a clinical isolate, we propose that the T6SS of A. baumannii is probably not involved in virulence; this idea is supported by multiple genomic analyses showing that the majority of clinical A. baumannii strains lack proteins essential to the T6SS. We also show that, unlike in other species, the C terminus of VgrG is a unique architectural requirement for functional T6SS assembly in A. baumannii, suggesting that over evolutionary time, bacteria have developed changes to their T6SS architecture, leading to specialized systems.
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14
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Gao Q, Meng X, Gu H, Chen X, Yang H, Qiao Y, Guo X. Two Phenotype-Differentiated Acinetobacter baumannii Mutants That Survived in a Meropenem Selection Display Large Differences in Their Transcription Profiles. Front Microbiol 2019; 10:2308. [PMID: 31649648 PMCID: PMC6794425 DOI: 10.3389/fmicb.2019.02308] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Accepted: 09/20/2019] [Indexed: 11/13/2022] Open
Abstract
37662RM1 and 37662RM2 are two phenotypically different, carbapenem-resistant mutants of Acinetobacter baumannii 37662 isolate following selection with meropenem (MEM) at sub-inhibitory concentrations. 37662RM2 lacks capsule synthesis and shows dramatically increased biofilm formation, while 37662RM1 shows merely impaired capsule synthesis. Here we report that 37662RM1 and RM2 have transcription profiles that are different from those of their starting strain, 37662WT. There were far more differentially expressed genes in 37662RM2 than in 37662RM1. The capsule polysaccharide (CPS) synthesis-required genes (itrA2, gtr5, psaA, psaB, psaC, psaD, psaE, psaF, kpsS2, wzx, wzy, wza, wzb, and wzc) showed reduced transcription levels in 37662RM2, which may at least partially explain the loss of capsule synthesis. The csu operon genes responsible for pili assembly and their regulator genes bfmR-bfmS were over-expressed in 37662RM2. This result together with the established critical roles of these genes in biofilm formation provide solid evidence that up-regulation of csu and bfmR-bfmS should be considered responsible for the enhanced biofilm formation in 37662RM2. ISAba1 was found to insert into the intergenic region between the csu operon and the acrR gene and should be responsible for the significant up-regulation of acrR, which was proposed to be associated with biofilm formation. Genome sequencing revealed that the ISAba1 upstream bla OXA- 508 (a new member of bla OXA- 51-like) and acrR were duplicated, suggesting a replicative transposition event. Altogether, the phenotype divergence driven by MEM selection mainly occurs at the RNA level and the transposition of ISAba1 plays an important role in modulating gene expression to adapt to the environment.
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Affiliation(s)
- Qianqian Gao
- Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Xiaobin Meng
- Meizhou People's Hospital, Meizhou, China.,Guangdong Provincial Key Laboratory of Precision Medicine and Clinical Translation Research of Hakka Population, Meizhou, China
| | - Hanfu Gu
- Meizhou People's Hospital, Meizhou, China.,Guangdong Provincial Key Laboratory of Precision Medicine and Clinical Translation Research of Hakka Population, Meizhou, China
| | - Xueqin Chen
- Meizhou People's Hospital, Meizhou, China.,Guangdong Provincial Key Laboratory of Precision Medicine and Clinical Translation Research of Hakka Population, Meizhou, China
| | - Huaqing Yang
- Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Yangyang Qiao
- Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Xuemin Guo
- Meizhou People's Hospital, Meizhou, China.,Guangdong Provincial Key Laboratory of Precision Medicine and Clinical Translation Research of Hakka Population, Meizhou, China.,Key Laboratory of Tropical Disease Control, Sun Yat-sen University, Ministry of Education, Guangzhou, China
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15
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Schramm STJ, Place K, Montaña S, Almuzara M, Fung S, Fernandez JS, Tuttobene MR, Golic A, Altilio M, Traglia GM, Vay C, Mussi MA, Iriarte A, Ramirez MS. Genetic and Phenotypic Features of a Novel Acinetobacter Species, Strain A47, Isolated From the Clinical Setting. Front Microbiol 2019; 10:1375. [PMID: 31275288 PMCID: PMC6591377 DOI: 10.3389/fmicb.2019.01375] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Accepted: 06/03/2019] [Indexed: 11/13/2022] Open
Abstract
In 2014, a novel species of Acinetobacter, strain A47, determined to be hospital-acquired was recovered from a single patient soft tissue sample following a traumatic accident. The complexity of the Acinetobacter genus has been established, and every year novel species are identified. However, specific features and virulence factors that allow members of this genus to be successful pathogens are not well understood. Utilizing both genomic and phenotypic approaches, we identified distinct features and potential virulence factors of the A47 strain to understand its pathobiology. In silico analyses confirmed the uniqueness of this strain and other comparative and sequence analyses were used to study the evolution of relevant features identified in this isolate. The A47 genome was further analyzed for genes associated with virulence and genes involved in type IV pili (T4P) biogenesis, hemolysis, type VI secretion system (T6SS), and novel antibiotic resistance determinants were identified. A47 exhibited natural transformation with both genomic and plasmid DNA. It was able to form biofilms on different surfaces, to cause hemolysis of sheep and rabbit erythrocytes, and to kill competitor bacteria. Additionally, surface structures with non-uniform length were visualized with scanning electron microscopy and proposed as pili-like structures. Furthermore, the A47 genome revealed the presence of two putative BLUF type photoreceptors, and phenotypic assays confirmed the modulation by light of different virulence traits. Taken together, these results provide insight into the pathobiology of A47, which exhibits multiple virulence factors, natural transformation, and the ability to sense and respond to light, which may contribute to the success of an A47 as a hospital dwelling pathogen.
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Affiliation(s)
- Sareda T. J. Schramm
- Department of Biological Science, California State University Fullerton, Fullerton, CA, United States
| | - Kori Place
- Department of Biological Science, California State University Fullerton, Fullerton, CA, United States
| | - Sabrina Montaña
- Facultad de Medicina, Instituto de Microbiología y Parasitología Médica (IMPaM, UBA-CONICET), Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Marisa Almuzara
- Laboratorio de Bacteriología Clínica, Departamento de Bioquímica Clínica, Hosp. de Clínicas José de San Martín, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Sammie Fung
- Department of Biological Science, California State University Fullerton, Fullerton, CA, United States
| | - Jennifer S. Fernandez
- Department of Biological Science, California State University Fullerton, Fullerton, CA, United States
| | - Marisel R. Tuttobene
- Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI – CONICET), Rosario, Argentina
| | - Adrián Golic
- Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI – CONICET), Rosario, Argentina
| | - Matías Altilio
- Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI – CONICET), Rosario, Argentina
| | - German M. Traglia
- Laboratorio de Bacteriología Clínica, Departamento de Bioquímica Clínica, Hosp. de Clínicas José de San Martín, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Carlos Vay
- Laboratorio de Bacteriología Clínica, Departamento de Bioquímica Clínica, Hosp. de Clínicas José de San Martín, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Maria Alejandra Mussi
- Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI – CONICET), Rosario, Argentina
| | - Andres Iriarte
- Laboratorio de Biología Computacional, Departamento de Desarrollo Biotecnológico, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Maria Soledad Ramirez
- Department of Biological Science, California State University Fullerton, Fullerton, CA, United States
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16
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Magallon J, Chiem K, Tran T, Ramirez MS, Jimenez V, Tolmasky ME. Restoration of susceptibility to amikacin by 8-hydroxyquinoline analogs complexed to zinc. PLoS One 2019; 14:e0217602. [PMID: 31141575 PMCID: PMC6541283 DOI: 10.1371/journal.pone.0217602] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Accepted: 05/14/2019] [Indexed: 11/18/2022] Open
Abstract
Gram-negative pathogens resistant to amikacin and other aminoglycosides of clinical relevance usually harbor the 6’-N-acetyltransferase type Ib [AAC(6')-Ib], an enzyme that catalyzes inactivation of the antibiotic by acetylation using acetyl-CoA as donor substrate. Inhibition of the acetylating reaction could be a way to induce phenotypic conversion to susceptibility in these bacteria. We have previously observed that Zn2+ acts as an inhibitor of the enzymatic acetylation of aminoglycosides by AAC(6')-Ib, and in complex with ionophores it effectively reduced the levels of resistance in cellulo. We compared the activity of 8-hydroxyquinoline, three halogenated derivatives, and 5-[N-Methyl-N-Propargylaminomethyl]-8-Hydroxyquinoline in complex with Zn2+ to inhibit growth of amikacin-resistant Acinetobacter baumannii in the presence of the antibiotic. Two of the compounds, clioquinol (5-chloro-7-iodo-8-hydroxyquinoline) and 5,7-diiodo-8-hydroxyquinoline, showed robust inhibition of growth of the two A. baumannii clinical isolates that produce AAC(6')-Ib. However, none of the combinations had any activity on another amikacin-resistant A. baumannii strain that possesses a different, still unknown mechanism of resistance. Time-kill assays showed that the combination of clioquinol or 5,7-diiodo-8-hydroxyquinoline with Zn2+ and amikacin was bactericidal. Addition of 8-hydroxyquinoline, clioquinol, or 5,7-diiodo-8-hydroxyquinoline, alone or in combination with Zn2+, and amikacin to HEK293 cells did not result in significant toxicity. These results indicate that ionophores in complex with Zn2+ could be developed into potent adjuvants to be used in combination with aminoglycosides to treat Gram-negative pathogens in which resistance is mediated by AAC(6')-Ib and most probably other related aminoglycoside modifying enzymes.
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Affiliation(s)
- Jesus Magallon
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, United States of America
| | - Kevin Chiem
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, United States of America
| | - Tung Tran
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, United States of America
| | - Maria S. Ramirez
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, United States of America
| | - Veronica Jimenez
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, United States of America
| | - Marcelo E. Tolmasky
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, United States of America
- * E-mail:
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