Resistance in nonfermenting gram-negative bacteria: multidrug resistance to the maximum

Antimicrobial Sensitivity Profile in Psittacine Birds at an Avian Teaching Hospital: A Retrospective Study, 2015-2022

Veterinary hospitals house patient populations with diverse infectious statuses, microbiota, and histories of prior antibiotic therapy. Choanal swabs are commonly used for assessing the upper respiratory tract of birds for bacterial disease, with the samples submitted for cytologic testing and/or culture and antimicrobial sensitivity testing. The aim of this retrospective study was to identify and quantify bacteria isolated from choanal swabs collected from psittacine patients at a veterinary teaching hospital in Mexico City, Mexico. Data regarding bacterial isolates from choanal swabs were obtained from the medical records of companion psittacines suspected of upper respiratory bacterial disease that presented between November 2015 and December 2022. A total of 47.8% (175 of 366) of the bacterial isolates were from specimens obtained from red-lored Amazons (Amazona autumnalis). Gram-negative bacteria predominated, with 27 different genera identified. Klebsiella, Staphylococcus, and Escherichia were the most frequently isolated genera. A total of 90.4% (331 of 366) of the isolates were resistant to at least 1 antibiotic tested in the sensitivity panel, and a single Klebsiella isolate was resistant to 13 different antibiotics. Gentamicin had a high percentage of efficacy (79.5%; 182 of 229) against the bacterial isolates, whereas isolates tested against sulfonamide-trimethoprim (46.7%, 98 of 210), streptomycin (43.8%; 88 of 201), and clindamycin (12.9%; 15 of 116) had susceptibilities <50%. This is the first study to report common bacterial isolates and their antimicrobial susceptibility patterns from choanal swab samples collected from companion psittacines suspected of upper respiratory disease in Mexico. Clinicians can use the information presented in this study as a guide for therapeutic decision-making when managing upper respiratory bacterial infections in companion psittacine patients.

Antibiotic persistence and its impact on the environment

From boon molecules to molecules contributing to rising concern has been the sojourn of antibiotics. The problem of antibiotic contamination has gotten worse due to antibiotics' pervasive use in every aspect of the environment. One such consequence of pollution is the increase in infections with antibiotic resistance. All known antimicrobials being used for human benefit lead to their repetitive and routine release into the environment. The misuse of antibiotics has aggravated the situation to a level that we are short of antibiotics to treat infections as organisms have developed resistance against them. Overconsumption is not just limited to human health care, but also occurs in other areas such as aquaculture, livestock, and veterinary applications for the purpose of improving feed and meat products. Due to their harmful effects on non-target species, the trace level of antibiotics in the aquatic ecosystem presents a significant problem. Since the introduction of antibiotics into the environment is more than their removal, they have been given the status of persistent pollutants. The buildup of antibiotics in the environment threatens aquatic life and may lead to bacterial strains developing resistance. As newer organisms are becoming resistant, there exists a shortage of antibiotics to treat infections. This has presented a very critical problem for the health-care community. Another rising concern is that the development of newer drug molecules as antibiotics is minimal. This review article critically explains the cause and nature of the pollution and the effects of this emerging trend. Also, in the latter sections, why we need newer antibiotics is questioned and discussed.

Examining the activity of cefepime-taniborbactam against Burkholderia cepacia complex and Burkholderia gladioli isolated from cystic fibrosis patients in the United States

The novel clinical-stage β-lactam-β-lactamase inhibitor combination, cefepime-taniborbactam, demonstrates promising activity toward many Gram-negative bacteria producing class A, B, C, and/or D β-lactamases. We tested this combination against a panel of 150 Burkholderia cepacia complex (Bcc) and Burkholderia gladioli strains. The addition of taniborbactam to cefepime shifted cefepime minimum inhibitory concentrations toward the provisionally susceptible range in 59% of the isolates tested. Therefore, cefepime-taniborbactam possessed similar activity as first-line agents, ceftazidime and trimethoprim-sulfamethoxazole, supporting further development.

Bloodstream gram-negative bacterial infections in adult patients with leukemia: A retrospective review of medical records in a tertiary care hospital in Western Saudi Arabia

BACKGROUND

Patients with neutropenic cancers are at high risk of acquiring infections, especially if on chemotherapy. Gram-negative bacterial infections are associated with high mortality. This study aimed to assess clinical characteristics, outcomes, and epidemiology of gram-negative bacterial (GNB) bloodstream infections (BSI) in adult patients with leukemia.

METHODS

This single-center, retrospective study included 102 adult patients diagnosed with leukemia between 2017 and 2019. The patients' demographics, infection diagnosis, leukemia diagnosis, comorbidities, and infection outcomes were collected from electronic medical records.

RESULTS

The most common GNB were Klebsiella pneumoniae (33.3 %), Pseudomonas aeruginosa (23.5 %), and Escherichia coli (17.6 %). Additionally, 36.7 % of infections were multidrug resistant. The most common comorbidities were cardiovascular diseases (36.7 %), diabetes mellitus (33.3 %), and liver diseases (24.1 %). GNB-infected patients had a higher mortality than noninfected patients (35.3 % and 11.8 %, respectively, p = 0.005). In a multivariable analysis, patients with acute myeloid leukemia and acute lymphoid leukemia were significantly more likely to acquire GNB BSI (p = 0.01), while patients with chronic myelogenous leukemia and chronic lymphocytic leukemia had a lower likelihood of developing GNB BSI. In addition, low hemoglobin level was an independent risk factor of GNB BSI (p = 0.001). Chemotherapeutic agents showed an association with increased risk of GNB BSI.

CONCLUSIONS

Patients with acute leukemia and low hemoglobin levels have increased risk of GNB BSI, which was associated with increased mortality. Prospective studies are needed to further assess the effect of co-morbidities and chemotherapy medications on the occurrence of GNB BSI according to the type of leukemia.

The Challenge of Bacteremia Treatment due to Non-Fermenting Gram-Negative Bacteria

Nosocomial infections caused by non-fermenting Gram-negative bacteria are a real challenge for clinicians, especially concerning the accuracy of empirical treatment. This study aimed to describe the clinical characteristic, empirical antibiotic therapy, accuracy of these prescriptions for appropriate coverage and risk factor for clinical failure of bloodstream infections due to non-fermenting Gram-negative bacilli. This retrospective, observational cohort study was conducted between January 2016 and June 2022. Data were collected from the hospital's electronic record. The statistic tests corresponding to each objective were applied. A multivariate logistic regression was performed. Among the total 120 patients included in the study, the median age was 63.7 years, and 79.2% were men. Considering the appropriate empirical treatment rate by species, inappropriate treatment for S. maltophilia was 72.4% (p = 0.088), for A. baumanii 67.6% and 45.6% for P. aeruginosa. Clinical success was achieved in 53.3%, and overall, 28-day mortality was 45.8%. ICU admission, sepsis or shock septic, age, previous antibiotic treatment and contact with healthcare facilities were independently associated with clinical failure. In conclusion, bloodstream infection produced by multidrug-resistant non-fermenting Gram-negative bacteria is a significant therapeutic management challenge for clinicians. The accuracy of empirical treatment is low due to the fact that it is not recommended to cover these microorganisms empirically, especially S. maltophilia and A. baumanii.

Chemical Profiling and Biological Properties of Essential Oils of Lavandula stoechas L. Collected from Three Moroccan Sites: In Vitro and In Silico Investigations

The aim of this study was the determination of the chemical compounds of Lavandula stoechas essential oil from Aknol (LSEO_A), Khenifra (LSEO_K), and Beni Mellal (LSEO_B), and the in vitro investigation of their antibacterial, anticandidal, and antioxidant effects, and in silico anti-SARS-CoV-2 activity. The chemical profile of LSEO was determined using GC-MS-MS analysis, the results of which showed a qualitative and quantitative variation in the chemical composition of volatile compounds including L-fenchone, cubebol, camphor, bornyl acetate, and τ-muurolol; indicating that the biosynthesis of essential oils of Lavandula stoechas (LSEO) varied depending on the site of growth. The antioxidant activity was evaluated using the ABTS and FRAP methods, our results showed that this tested oil is endowed with an ABTS inhibitory effect and an important reducing power which varies between 4.82 ± 1.52 and 15.73 ± 3.26 mg EAA/g extract. The results of antibacterial activity of LSEO_A, LSEO_K and LSEO_B, tested against Gram-positive and Gram-negative bacteria, revealed that B. subtilis (20.66 ± 1.15-25 ± 4.35 mm), P. mirabilis (18.66 ± 1.15-18.66 ± 1.15 mm), and P. aeruginosa (13.33 ± 1.15-19 ± 1.00 mm) are the most susceptible strains to LSEO_A, LSEO_K and LSEO_B of which LSEO_B exhibits bactericidal effect against P. mirabilis. furthermore The LSEO exhibited varying degrees of anticandidal activity with an inhibition zones of 25.33 ± 0.5, 22.66 ± 2.51, and 19 ± 1 mm for LSEO_K, LSEO_B, and LSEO_A, respectively. Additionally, the in silico molecular docking process, performed using Chimera Vina and Surflex-Dock programs, indicated that LSEO could inhibit SARS-CoV-2. These important biological properties of LSEO qualify this plant as an interesting source of natural bioactive compounds with medicinal actions.

Drug Resistance among Major Non-fermenting Gram-negative Pathogens Isolated from Respiratory Tract Infections in a Tertiary Care Hospital of South Karnataka

Non-fermenting gram-negative bacteria (NFGNB) frequently exhibit drug resistance. The purpose of this study was to determine the drug resistance pattern among the NFGNB isolates causing respiratory tract infections (RTIs). A retrospective analysis of the antimicrobial susceptibility pattern of non-fermenters causing RTIs over four years (2016- 2019) was done and the change in drug resistance pattern was studied. A total of 653 cases were obtained that included 191 (29.2%) Moraxella catarrhalis, 283 (43.3%) Pseudomonas aeruginosa, and 132 (20.2%) Acinetobacter baumannii, 47 (7.2%) Stenotrophomonas maltophilia isolates. A higher resistance (82.6%) was observed for piperacillin-tazobactam and cefpirome, followed by imipenem (79.5%) and ciprofloxacin (76.5 %) for A. baumannii isolates. A sharp decline in resistance pattern for piperacillin, cefpirome, Imipenem and cefoperazone-sulbactam in 2019 and an increasing resistance to gentamycin and ciprofloxacin were noted. Among P. aeruginosa isolates, 94% aztreonam and 83.4% cefoperazone-sulbactam resistance were detected. There was an increased resistance for cefpirome and piperacillin and a decreased resistance for Imipenem was recorded in 2019. In cases of M. catarrhalis, 22.51% of isolates were resistant to ciprofloxacin, followed by erythromycin (18.32%) and tetracycline (17.80 %). S. maltophilia showed a 100% sensitivity for co-trimoxazole and 2.1% resistance for ciprofloxacin. A constantly changing antibiotic-resistant pattern of non-fermenters compels for a continuous update of drug-resistant trends through a longitudinal surveillance program in different geographical areas.

Marine Based Natural Products: Exploring the Recent Developments in the Identification of Antimicrobial Agents

The marine ecosystem is the less explored, biologically diverse, and vastest resource to discover novel antimicrobial agents. In recent decades' antimicrobial drugs are losing their effectiveness due to the growing resistance among pathogens, which causes diseases to have considerable death rates across the globe. Therefore, there is a need for the discovery of new antibacterials that can reach the market. There is a gradual growth of compounds from marine sources which are entering the clinical trials. Thus, the prominence of marine natural products in the field of drug design and discovery across the academia and pharmaceutical industry is gaining attention. Herein,  the present review covers nearly 200 marine based antimicrobial agents of 11 structural classes discovered from the year 2010 to 2022. All the discussed compounds have exhibited medium to high antimicrobial activity in inhibiting various microorganisms.

Bacterial contamination of neglected hospital surfaces and equipment in an Algerian hospital: an important source of potential infection

Hospital surfaces are heavily contaminated with bacteria, which are a potential source of nosocomial infections. This study was undertaken to identify bacterial communities isolated from neglected hospital surfaces after cleaning routine in a Algerian public hospital. Screening of bacterial contamination in patient bed (PB), reception land-line phones (TF), door handles (DH) and medical equipment (ME) during five months generated 108 inocula. Isolates obtained were identified based on biochemical characteristics and confirmed by analysis of 16S rRNA sequences. Statistical analysis was performed to reveal possible relationship between bacterial diversity and swabbed surfaces. Our findings showed a high prevalence of bacteria in various hospital surfaces, reaching (65.25%), where a highest contaminated surface was the PB (47.22%) and a lowest contaminated was TF (5.55%). Gram negative bacteria were the dominant group (62.03%) mainly represented by Entrobacteriaceae (42.59%), whereas Staphylococcus aureus belonging to Gram positive was the main expanded pathogen with (15.74%).

Interactions between polymyxin B and various bacterial membrane mimics: A molecular dynamics study

Polymyxin B (PMB) is clinically used as a last-line therapy against life-threatening Gram-negative "superbugs". However, thorough understanding of the membrane actions of PMB at a molecular level is still lacking. In this work, a variety of bacterial membrane mimics with varying lipid compositions were built, and their interactions with PMB were systematically investigated using coarse-grained molecular dynamics simulation. PMB demonstrated characteristic preference to specific lipid species during its interaction with different membrane systems, such as the rough mutant lipipolysacchrides (Re LPS) preference in an outer membrane (OM) or the cardiolipin and POPG affinity in an inner membrane (IM). As a result of the lipid-specific actions, complicated membrane interaction states of PMB were observed, including adsorption on the OM surface. In contrast, for the IM or a mutative OM containing "impurity lipids" like POPE, POPG or lipid A, it could insert into the membrane via its acyl chain. Such actions of PMB influence the structure and lipid mobility of the membrane. In particular, the OM-bound PMB breaks the synchronous movement of Re LPS molecules in the outer leaflet and makes them diffuse more randomly, while its insertion into IM blocks the phospholipid diffusion and makes the membrane more homogeneous in the trajectory space. Our results provide insight into the action mechanism of PMB at a membrane level and a foundation for developing novel and safer polymyxin strategies for better clinical use.

Antimicrobial susceptibility pattern of Burkholderia cepacia complex & Stenotrophomonas maltophilia from North India: Trend over a decade (2007-2016)

Background & objectives

With increased isolation of Burkholderia cepacia complex (Bcc) and Stenotrophomonas maltophilia from clinical specimens, knowledge of their antimicrobial susceptibility trend will aid in better patient management. This study provides a comprehensive picture of this trend over a decade.

Methods

A retrospective analysis of laboratory records over 10 years for antimicrobial susceptibility pattern of Bcc and S. maltophilia was carried out. The susceptibility pattern to commonly used antimicrobials was determined using disk diffusion and compared at the beginning, mid and end of the study period.

Results

Five hundred and thirty Bcc and 665 S. maltophilia isolated over the past 10 yr were included in the study. Over the years, susceptibility of Bcc for co-trimoxazole varied as 80, 70 and 89 per cent at the beginning, middle and end of the study, respectively. Susceptibility to tetracycline was 43 per cent at the beginning of the study and that to minocycline was 100 per cent mid-study and 74 per cent at the end. Susceptibility to ceftazidime varied as 83, 60 and 65 per cent, respectively, and to meropenem, increased during the first half of the study and decreased in the second half, as 60, 70 and 43 per cent, respectively. Bcc susceptibility to levofloxacin decreased from 84 (in 2014) to 76 per cent (in 2016). S. maltophilia susceptibility to co-trimoxazole varied as 90, 82 and 87 per cent, respectively, whereas that to levofloxacin was 80, 100 and 94 per cent, respectively, during the start, mid and end of the study. Susceptibility to minocycline decreased from 100 per cent mid-study to 96 per cent at the end. Susceptibility of S. maltophilia to ceftazidime increased from 24 (in 2012) to 37 per cent (in 2016). All variations among the three phases of the study were significant for all antimicrobials tested for both the organisms.

Interpretation & conclusions

While Bcc showed increased resistance to ceftazidime, meropenem and minocycline, S. maltophilia maintained >80 per cent susceptibility to minocycline, levofloxacin and co-trimoxazole throughout the decade. By 2016, Bcc was most susceptible to co-trimoxazole, whereas S. maltophilia was most susceptible to minocycline and levofloxacin.

Prevalence and antibiogram of non-fermenting Gram-negative bacilli in blood stream infections: Study in a tertiary care centre, Western Uttar Pradesh, India

Non-fermenting Gram-negative bacilli (NFGNB) are emerging as important cause of blood stream infections. We aimed to determine the prevalence and antibiotic susceptibility pattern of NFGNB isolated from blood of patients with sepsis. We found, in 176 patients, the most common to be Pseudomonas aeruginosa (74) and Acinetobacter baumanii complex (39) followed by Stenotrophomonas maltophilia (16), Sphingomonas paucimobilis (6), Burkholderia cepacia (5) and Ochrobactrum anthropic (1). Generally, organisms showed a good sensitivity towards colistin, carbapenems and fluoroquinolones, whereas cephalosporins were ineffective.

GC-MS Analysis, Antioxidant and Antimicrobial Activities of Achillea Odorata Subsp. Pectinata and Ruta Montana Essential Oils and Their Potential Use as Food Preservatives

In order to discover new natural resources with biological properties, the chemical composition, the antioxidant and antimicrobial activities, and the potential use as food preservative of essential oils of Moroccan Achillea odorata subsp. pectinata (AO_pEO) and Ruta montana (RMEO) were studied. Gas chromatography-mass spectrometry (GC-MS) analysis revealed the presence of 21 and 25 compounds in AO_pEO and RMEO, respectively. The results showed that the major compounds of AO_pEO are camphor (45.01%), bornyl acetate (15.07%), borneol (11.33%), β-eudesmol (4.74%), camphene (3.58%), and 1.8-cineole (eucalyptol) (2.96%), whereas 2-undecanone (63.97%), camphor (3.82%) and cyclopropanecarboxylic acid (3.66%) were the main components of RMEO. The antioxidant activities were evaluated by diphenylpicrylhydraziyl radical (DPPH) and reducing power assays. The antimicrobial activities of essential oils were tested against bacterial strains and food contaminant yeast using agar disc diffusion and microdilution methods. A significant antimicrobial activity of AO_pEO was observed against Bacillus subtilis, Proteus mirabilis and Candida albicans, compared to RMEO. The efficacy of AO_pEO was also evaluated in model food systems (cabbage and barley) artificially inoculated during storage. The results found that the adding of a minimal inhibitory concentration (MIC) and 4× MIC were potent in decreasing the Proteus mirabilis growth in food model systems. Our findings suggested that AO_pEO may be potentially used as an alternative food preservative.

Natural killer cells kill Burkholderia cepacia complex via a contact-dependent and cytolytic mechanism

Burkholderia cepacia complex (Bcc), which includes B. cenocepacia and B. multivorans, pose a life-threatening risk to patients with cystic fibrosis. Eradication of Bcc is difficult due to the high level of intrinsic resistance to antibiotics, and failure of many innate immune cells to control the infection. Because of the pathogenesis of Bcc infections, we wondered if a novel mechanism of microbial host defense involving direct antibacterial activity by natural killer (NK) cells might play a role in the control of Bcc. We demonstrate that NK cells bound Burkholderia, resulting in Src family kinase activation as measured by protein tyrosine phosphorylation, granule release of effector proteins such as perforin and contact-dependent killing of the bacteria. These studies provide a means by which NK cells could play a role in host defense against Bcc infection.

How Phages Overcome the Challenges of Drug Resistant Bacteria in Clinical Infections

Nowadays the most important problem in the treatment of bacterial infections is the appearance of MDR (multidrug-resistant), XDR (extensively drug-resistant) and PDR (pan drug-resistant) bacteria and the scarce prospects of producing new antibiotics. There is renewed interest in revisiting the use of bacteriophage to treat bacterial infections. The practice of phage therapy, the application of phages to treat bacterial infections, has been around for approximately a century. Phage therapy relies on using lytic bacteriophages and purified phage lytic proteins for treatment and lysis of bacteria at the site of infection. Current research indicates that phage therapy has the potential to be used as an alternative to antibiotic treatments. It is noteworthy that, whether phages are used on their own or combined with antibiotics, phages are still a promising agent to replace antibiotics. So, this review focuses on an understanding of challenges of MDR, XDR, and PDR bacteria and phages mechanism for treating bacterial infections and the most recent studies on potential phages, cocktails of phages, and enzymes of lytic phages in fighting these resistant bacteria.

Antibiotic resistance genes identified in wastewater treatment plant systems - A review

The intensive use of antibiotics for human, veterinary and agricultural purposes, results in their continuous release into the environment. Together with antibiotics, antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are introduced into wastewater. Wastewater treatment plants (WWTPs) are believed to be probable hotspots for antibiotic resistance dissemination in the environment as they offer convenient conditions for ARB proliferation as well as for horizontal transfer of ARGs among different microorganisms. In fact, genes conferring resistance to all classes of antibiotics together with mobile genetic elements (MGEs) like plasmids, transposons, bacteriophages, integrons are detected in WWTPs in different countries. It seems that WWTPs with conventional treatment processes are capable of significant reduction of ARB but are not efficient in ARG removal. Implementation of advanced wastewater cleaning processes in addition to a conventional wastewater treatment is an important step to protect the aquatic environment. Growing interest in presence and fate of ARB and ARGs in WWTP systems resulted in the fact that knowledge in this area has increased staggeringly in the past few years. The main aim of the article is to collect and organize available data on ARGs, that are commonly detected in raw sewage, treated wastewater or activated sludge. Resistance to the antibiotics usually used in antibacterial therapy belonging to main classes like beta-lactams, macrolides, quinolones, sulfonamides, trimethoprim and tetracyclines was taken into account. The presence of multidrug efflux genes is also included in this paper. The occurrence of antibiotics may promote the selection of ARB and ARGs. As it is important to discuss the problem considering all aspects that influence it, the levels of antibiotics detected in influent and effluent of WWTPs were also presented.

Emergence of Multidrug- and Pandrug- Resistant Pseudomonas aeruginosa from Five Hospitals in Qatar

Background

A global rise in multidrug-resistant (MDR) nosocomial infections has led to a significant increase in morbidity and mortality. MDR Gram-negative bacteria (GNB) are recognised for rapidly developing drug resistance. Despite Pseudomonas aeruginosa being the second most common GNB isolated from healthcare associated infections, the magnitude of MDR P. aeruginosa (MDR-PA) has not been evaluated in Qatar.

Aim

To assess the prevalence and antimicrobial susceptibility patterns of MDR-PA from 5 major hospitals in Qatar.

Methods

A total of 2533 P. aeruginosa clinical isolates were collected over a one-year period. MDR-PA was defined as resistance to at least one agent of ≥ 3 antibiotic classes. Clinical and demographic data were collected prospectively.

Findings

The overall prevalence of MDR-PA isolates was 8.1% (205/2533); the majority of isolates were from patients exposed to antibiotics during 90 days prior to isolation (85.4 %, 177/205), and the infections were mainly hospital-acquired (95.1%, 195/205) with only 4.9% from the community. The majority of MDR-PA isolates were resistant to cefepime (96.6%, 198/205), ciprofloxacin, piperacillin/tazobactam (91%, 186/205), and meropenem (90%, 184/205). Patient comorbidities with MDR-PA were diabetes mellitus (47.3%, n=97), malignancy (17.1%, n=35), end-stage renal disease (13.7%, n=28) and heart failure (10.7%, n=22).

Conclusion

There was a significant prevalence of MDR-PA in Qatar, primarily from healthcare facilities and associated with prior antibiotic treatment. There was an alarming level of antimicrobial resistance to carbapenems. Our results are part of a national surveillance of MDR to establish effective containment plans.

High Prevalence of Multi-Drug Resistance and Extended Spectrum Beta Lactamase Production in Non-Fermenting Gram-Negative Bacilli in Ethiopia

BACKGROUND

Emergence of resistance to multiple antimicrobial agents in Non-Fermenting Gram-Negative Bacilli is a major problem to public health, as it limits drug treatment options against infections. The aim of this study was to determine the prevalence of multi-drug resistance and extended spectrum beta lactamase production in Non-Fermenting Gram-Negative Bacilli.

MATERIALS AND METHODS

Different clinical samples were collected and processed following standard procedures. Each sample was then inoculated onto culture media. Identification, drug susceptibility testing, and extended spectrum beta lactamase production of the isolates were carried out by using the VITEK 2 compact system.

RESULTS

Among 996 clinical samples, 135 samples yielded Non-Fermenting Gram-Negative Bacilli of which Pseudomonas and Acinetobacter species were the commonest isolates. The overall drug resistance rates of Non-Fermenting Gram-Negative Bacilli were above 80% against ampicillin (89.6%), cefuroxime axetil (88.9%), nitrofurantoin (85.9%), cefalotin (84.4%), cefoxitin (83.7%), cefazolin (83.0%), and cefuroxime (83.0%). Tobramycin with a resistance rate of 19.3% was the most active antimicrobial agent. Out of 135 isolates, 81.5% were multi-drug resistant of which 13.3% were extensively drug resistant and 10.4% were pandrug resistant. Extended spectrum beta lactamase production was detected in 48.9% of the isolates.

CONCLUSIONS

The spectrum of bacterial species isolated was diverse. The isolates demonstrated high level of drug resistance in different classes of antibiotics. The magnitude of multi-drug resistance and the level of extended spectrum beta lactamase production were high. Hence, further studies on multi-drug resistant and extended spectrum beta lactamase producing Non-Fermenting Gram-Negative Bacilli both in the community and in hospital setting are essential.

Occurrence of Antibiotic-Resistant Bacteria in Therapy Pools and Surrounding Surfaces

The number of patients colonized with antibiotic-resistant bacteria is increasing in health care facilities. Because transmission of antibiotic-resistant bacteria is feared, there exist reports that the affected patients are frequently excluded from hydrotherapy, which is a non-invasive and beneficial treatment used for patients with different diseases. Data from the literature suggest that deficient water disinfection measures exist, which are not always sufficient to kill all released bacteria. If the pool water is not disinfected properly, it may also infect the bathers. Immunocompromised patients are particularly susceptible to be infected with (antibiotic-resistant) bacteria. In order to determine the distribution of antibiotic-resistant bacteria in the pool water treatment system and the pool environment and to estimate the associated transmission risk we analyzed samples from eleven health care facilities. Antibiotic-resistant bacteria were found in the water and surface samples collected. One hundred and two antibiotic-resistant isolates from water samples and 307 isolates from surrounding surfaces were obtained, respectively. The majority of the isolates belonged to non-fermenting Gram-negative rods, like Pseudomonas spp. Some isolates were resistant to a wide range of the tested antibiotics. The results indicate a relation between the number of isolates in water samples and the number of patients using the pools in combination with deficiencies in water treatment. In the pool environment the highest number of isolates was obtained from barefoot areas and floor cleaning equipment.

Antibacterial effect of silver nanoparticles in Pseudomonas aeruginosa

Pseudomonas aeruginosa has great intrinsic antimicrobial resistance limiting the number of effective antibiotics. Thus, other antimicrobial agents such as silver nanoparticles (AgNPs) are considered potential agents to help manage and prevent infections. AgNPs can be used in several applications against bacteria resistant to common antibiotics or even multi-resistant bacteria such as P. aeruginosa. This study assessed the antimicrobial activity of commercial 10 nm AgNPs on two hospital strains of P. aeruginosa resistant to a large number of antibiotics and a reference strain from a culture collection. All strains were susceptible to 5 µg/mL nanoparticles solution. Reference strains INCQS 0230 and P.a.1 were sensitive to AgNPs at concentrations of 1.25 and 0.156 µg/mL, respectively; however, this was not observed for hospital strain P.a.2, which was more resistant to all antibiotics and AgNPs tested. Cytotoxicity evaluation indicated that AgNPs, up to a concentration of 2.5 µg/mL, are very safe for all cell lines tested. At 5.0 µg/mL, AgNPs had a discrete cytotoxic effect on tumor cells HeLa and HepG2. Results showed the potential of using AgNPs as an alternative to conventional antimicrobial agents that are currently used, and a perspective for application of nanosilver with antibiotics to enhance antimicrobial activity.

EpideMiology and control measures of outBreaks due to Antibiotic-Resistant orGanisms in EurOpe (EMBARGO): a systematic review protocol

INTRODUCTION

Improving our understanding of outbreaks due to antibiotic-resistant bacteria (ARB) and their control is critical in the current public health scenario. The threat of outbreaks due to ARB requires multifaceted efforts. However, a global overview of epidemiological characteristics of outbreaks due to ARB and effective infection control measures is missing. In this paper, we describe the protocol of a systematic review aimed at mapping and characterising the epidemiological aspects of outbreaks due to ARB and infection control measures in European countries.

METHODS AND ANALYSIS

The databases MEDLINE, Web of Knowledge and Cochrane library will be searched using a 3-step search strategy. Selection of articles for inclusion will be performed by 2 reviewers using predefined eligibility criteria. All study designs will be included if they report an outbreak and define the microbiological methods used for microorganism identification. The target bacteria will be methicillin-resistant and vancomycin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus, ceftazidime-resistant and carbapenem-resistant Acinetobacter baumannii, ceftazidime-resistant and carbapenem-resistant Pseudomonas aeruginosa, ciprofloxacin-resistant Escherichia coli, extended-spectrum β-lactamase-producing E. coli and Klebsiella pneumoniae, carbapenem-resistant and carbapenamase-producing Enterobacteriaceae. Data will be extracted using a tailored pilot tested form and the quality of reporting will be assessed using the ORION (Outbreak Reports and Intervention Studies Of Nosocomial infections) tool. Data will be synthesised and reported by the type of ARB, setting and country. Infection control measures and bundles of measures will be described. The effectiveness will be reported as defined by the authors. Regression analysis will be used to define independent factors associated with outbreaks' control. Heterogeneity between studies will be assessed by forest plots and I² statistics.

ETHICS AND DISSEMINATION

Ethical approval is not applicable for this study. Findings will be disseminated through journal publication and conference presentations and talks.

An Investigation of Antibacterial Resistance Patterns Among Acinetobacter baumannii and Pseudomonas aeruginosa Isolates Collected from Intensive Care Units of a University-Affiliated Hospital in Ahvaz, Iran

BACKGROUND

In recent decades, multidrug-resistant non-fermenting Gram-negative pathogens, particularly Acinetobacter baumannii and Pseudomonas aeruginosa, have been recognized as a major cause of healthcare-associated and nosocomial infections and outbreaks.

OBJECTIVES

The aim of this study was to determine the prevalence and pattern of antibiotic resistance in A. baumannii and P. aeruginosa isolates collected from intensive care units (ICUs).

METHODS

One hundred fifty-five clinical isolates, including 80 (51.6%) isolates of A. baumannii and 75 (48.4%) isolates of P. aeruginosa, from hospitalized patients in the ICUs of a teaching hospital in Ahvaz, Iran, were collected from January 1 to December 30, 2013. The organisms were identified with conventional bacteriological methods, and antimicrobial susceptibility testing was performed on all isolates in accordance with clinical laboratory and standards institute (CLSI) guidelines.

RESULTS

The maximum resistance rates among A. baumannii isolates were observed for ciprofloxacin and trimethoprim-sulfamethoxazole (96.9% and 95.2%, respectively). For P. aeruginosa isolates, the maximum resistance rates were reported for ceftriaxone and trimethoprim-sulfamethoxazole (97.2% and 92.4%, respectively).

CONCLUSIONS

The majority of A. baumannii and P. aeruginosa isolates were found to be resistant to commonly recommended antibiotics. Therefore, surveillance of antibiotic consumption and proper antibiotic administration guidelines are essential for preventing major outbreaks in the future.

Report on the newly emerging nosocomial Burkholderia cepacia in a tertiary hospital

BACKGROUND

Burkholderia cepacia is an aerobic, motile, opportunistic Gram negative bacillus that can survive in certain disinfectants. This is a report of the emerging infection with the bacteria B. cepacia in our hospital. The awareness of this emerging bacterium is important, as it is known to cause nosocomial infection in hospitals, especially in the Intensive Care Unit (ICU) setting. setting. B. cepacia, although known to be multidrug resistant, shows sensitivity to some antibiotics that can be used to treat infection caused by it.

METHODS

The cases of infection and antimicrobial susceptibility of nosocomial B. cepacia pattern have been analyzed.

RESULTS

A total of 38 cases with B. cepacia infection were isolated. Two of these cases showed the organism in two samples, totalling the sample collection to 40. The most frequent isolation of B. cepacia was from blood 21/40 (52.5%) and pus 9/40 (22.5%). B. cepacia infections were most commonly observed in the Intensive Care Unit (52.6%). Infections were more common in men than women with a mortality rate of 42%. The most sensitive antimicrobial agents were found to be Colistin (93%) and Cotrimoxazole (71%).

CONCLUSION

There have been 38 cases of the emerging nosocomial B. cepacia infection in our hospital in the period from September 2012 to February 2014. There was no case reported in the records before September 2012. Infections caused by B. cepacia should be made aware of and taken seriously because of its high transmissibility, intrinsic resistance to antibiotics, high mortality and most importantly its sensitivity to simple antibiotics such as Cotrimoxazole.

Thiolactomycin-Based Inhibitors of Bacterial β-Ketoacyl-ACP Synthases with in Vivo Activity

β-Ketoacyl-ACP synthases (KAS) are key enzymes involved in the type II bacterial fatty acid biosynthesis (FASII) pathway and are putative targets for antibacterial discovery. Several natural product KAS inhibitors have previously been reported, including thiolactomycin (TLM), which is produced by Nocardia spp. Here we describe the synthesis and characterization of optically pure 5R-thiolactomycin (TLM) analogues that show improved whole cell activity against bacterial strains including methicillin-resistant Staphylococcus aureus (MRSA) and priority pathogens such as Francisella tularensis and Burkholderia pseudomallei. In addition, we identify TLM analogues with in vivo efficacy against MRSA and Klebsiella pneumoniae in animal models of infection.

Mortality attributable to carbapenem-resistant Pseudomonas aeruginosa bacteremia: a meta-analysis of cohort studies

Whether carbapenem resistance is associated with mortality in patients with Pseudomonas aeruginosa bacteremia is controversial. To address this issue, we conducted a systematic review and meta-analysis based on cohort studies. We searched PubMed and Embase databases to identify articles (up to April 2015). The DerSimonian and Laird random-effect model was used to generate a summary estimate of effect. Associations were evaluated in subgroups based on different patient characteristics and study quality criteria. Seven studies with a total of 1613 patients were finally included, of which 1 study had a prospective design, and the other 6 were retrospective. Our meta-analysis showed patients with carbapenem-resistant P. aeruginosa bacteremia were at a higher risk of death compared with those with carbapenem-susceptible P. aeruginosa bloodstream infections (pooled odds ratio (OR) from three studies reporting adjusted ORs: 3.07, 95% confidence interval (CI), 1.60-5.89; pooled OR from 4 studies only reporting crude ORs: 1.46, 95% CI, 1.10-1.94). The results were robust across a number of stratified analyses and a sensitivity analysis. We also calculated that 8%-18.4% of deaths were attributable to carbapenem resistance in four studies assessing the outcome with 30-day mortality, and these were 3% and 14.6%, respectively, in two studies using 7-day mortality or mortality during bacteremia as an outcome of interest. Carbapenem resistance had a deleterious impact on the mortality of P. aeruginosa bacteremia; however, the results should be interpreted cautiously because only three studies reporting adjusted ORs were included. More large-scale, well-designed prospective cohorts, as well as mechanistic studies, are urgently needed in the future.

Repeated Burkholderia cepacia Peritonitis in a Patient Undergoing Continuous Ambulatory Peritoneal Dialysis

Burkholderia cepacia (B cepacia) is a rare opportunistic pathogen in continuous ambulatory peritoneal dialysis (CAPD) peritonitis. We describe the first case of repeated B cepacia CAPD peritonitis, occurring in an outpatient environment, treated with antimicrobial medication without peritoneal catheter removal. B cepacia may lead to repeat infection, therefore, we should insist on catheter removal during each peritonitis episode.

Efflux pump-mediated drug resistance in Burkholderia

Several members of the genus Burkholderia are prominent pathogens. Infections caused by these bacteria are difficult to treat because of significant antibiotic resistance. Virtually all Burkholderia species are also resistant to polymyxin, prohibiting use of drugs like colistin that are available for treatment of infections caused by most other drug resistant Gram-negative bacteria. Despite clinical significance and antibiotic resistance of Burkholderia species, characterization of efflux pumps lags behind other non-enteric Gram-negative pathogens such as Acinetobacter baumannii and Pseudomonas aeruginosa. Although efflux pumps have been described in several Burkholderia species, they have been best studied in Burkholderia cenocepacia and B. pseudomallei. As in other non-enteric Gram-negatives, efflux pumps of the resistance nodulation cell division (RND) family are the clinically most significant efflux systems in these two species. Several efflux pumps were described in B. cenocepacia, which when expressed confer resistance to clinically significant antibiotics, including aminoglycosides, chloramphenicol, fluoroquinolones, and tetracyclines. Three RND pumps have been characterized in B. pseudomallei, two of which confer either intrinsic or acquired resistance to aminoglycosides, macrolides, chloramphenicol, fluoroquinolones, tetracyclines, trimethoprim, and in some instances trimethoprim+sulfamethoxazole. Several strains of the host-adapted B. mallei, a clone of B. pseudomallei, lack AmrAB-OprA, and are therefore aminoglycoside and macrolide susceptible. B. thailandensis is closely related to B. pseudomallei, but non-pathogenic to humans. Its pump repertoire and ensuing drug resistance profile parallels that of B. pseudomallei. An efflux pump in B. vietnamiensis plays a significant role in acquired aminoglycoside resistance. Summarily, efflux pumps are significant players in Burkholderia drug resistance.

Clinical and in vitro evidence for the antimicrobial therapy in Burkholderia cepacia complex infections

Treatment of infections caused by Burkholderia cepacia complex (Bcc) in cystic fibrosis (CF) patients poses a complex problem. Bcc is multidrug-resistant due to innate and acquired mechanisms of resistance. As CF patients receive multiple courses of antibiotics, susceptibility patterns of strains from CF patients may differ from those noted in strains from non-CF patients. Thus, there was a need for assessing in vitro and clinical data to guide antimicrobial therapy in these patients. A systematic search of literature, followed by extraction and analysis of available information from human and in vitro studies was done. The results of the analysis are used to address various aspects like use of antimicrobials for pulmonary and non-pulmonary infections, use of combination versus monotherapy, early eradication, duration of therapy, route of administration, management of biofilms, development of resistance during therapy, pharmacokinetics-pharmacodynamics correlations, therapy in post-transplant patients and newer drugs in Bcc-infected CF patients.

Magnetic fields suppress Pseudomonas aeruginosa biofilms and enhance ciprofloxacin activity

Due to the refractory nature of pathogenic microbial biofilms, innovative biofilm eradication strategies are constantly being sought. Thus, this study addresses a novel approach to eradicate Pseudomonas aeruginosa biofilms. Magnetic nanoparticles (MNP), ciprofloxacin (Cipro), and magnetic fields were systematically evaluated in vitro for their relative anti-biofilm contributions. Twenty-four-hour biofilms exposed to aerosolized MNPs, Cipro, or a combination of both, were assessed in the presence or absence of magnetic fields (Static one-sided, Static switched, Oscillating, Static + oscillating) using changes in bacterial metabolism, biofilm biomass, and biofilm imaging. The biofilms exposed to magnetic fields alone exhibited significant metabolic and biomass reductions (p < 0.05). When biofilms were treated with a MNP/Cipro combination, the most significant metabolic and biomass reductions were observed when exposed to static switched magnetic fields (p < 0.05). The exposure of P. aeruginosa biofilms to a static switched magnetic field alone, or co-administration with MNP/Cipro/MNP + Cipro appears to be a promising approach to eradicate biofilms of this bacterium.

Interplay between intrinsic and acquired resistance to quinolones in Stenotrophomonas maltophilia

To analyse whether the mutation-driven resistance-acquisition potential of a given bacterium might be a function of its intrinsic resistome, quinolones were used as selective agents and Stenotrophomonas maltophilia was chosen as a bacterial model. S. maltophilia has two elements - SmQnr and SmeDEF - that are important in intrinsic resistance to quinolones. Using a battery of mutants in which either or both of these elements had been removed, the apparent mutation frequency for quinolone resistance and the phenotype of the selected mutants were found to be related to the intrinsic resistome and also depended on the concentration of the selector. Most mutants had phenotypes compatible with the overexpression of multidrug efflux pump(s); SmeDEF overexpression was the most common cause of quinolone resistance. Whole genome sequencing showed that mutations of the SmeRv regulator, which result in the overexpression of the efflux pump SmeVWX, are the cause of quinolone resistance in mutants not overexpressing SmeDEF. These results indicate that the development of mutation-driven antibiotic resistance is highly dependent on the intrinsic resistome, which, at least for synthetic antibiotics such as quinolones, did not develop as a response to the presence of antibiotics in the natural ecosystems in which S. maltophilia evolved.

Multi-drug-resistant, non-fermenting, gram-negative bacilli in neonatal sepsis in Kolkata, India: a 4-year study

BACKGROUND

Non-fermenting gram-negative bacilli (NFGNB) are an emerging problem in neonatal sepsis. A major concern is multi-drug resistance which severely limits treatment options.

AIMS AND OBJECTIVES

A retrospective observational study was conducted to analyse the role of non-fermenters in neonatal sepsis over a 4-year period, the factors leading to this trend and the pattern of antibiotic resistance.

METHODS

Demographic and clinical data were collected for all neonates with blood culture-positive sepsis during the study period, January 2007 to December 2010.

RESULTS

Blood cultures were positive in 186 (13%) of 1402 neonates, in 44 (32.1%) of whom the cause was NFGNB. Acinetobacter spp was the most common organism (n = 30). Infection by NFGNB showed a steady increase (P<0.0001), and was fairly evenly distributed between early- and late-onset sepsis. The infection rate was significantly higher in inborn neonates (P = 0.04) and those delivered vaginally (P = 0.002). Multi-drug resistance (MDR) occurred in 50% and carbapenem resistance in 30% of Acinetobacter spp isolates. In five cases there was panresistance of Acinetobacter spp to all antibiotics tested.

CONCLUSION

The trend of increasing numbers of cases of NFGNB in neonatal sepsis compounded by MDR is of great concern. It is necessary to administer antibiotics judiciously, strengthen surveillance and laboratory services in neonatal intensive care units, and re-evaluate treatment guidelines for management of infection by these organisms.

Management and prevention of ventilator-associated pneumonia caused by multidrug-resistant pathogens

Ventilator-associated pneumonia (VAP) due to multidrug-resistant (MDR) pathogens is a leading healthcare-associated infection in mechanically ventilated patients. The incidence of VAP due to MDR pathogens has increased significantly in the last decade. Risk factors for VAP due to MDR organisms include advanced age, immunosuppression, broad-spectrum antibiotic exposure, increased severity of illness, previous hospitalization or residence in a chronic care facility and prolonged duration of invasive mechanical ventilation. Methicillin-resistant Staphylococcus aureus and several different species of Gram-negative bacteria can cause MDR VAP. Especially difficult Gram-negative bacteria include Pseudomonas aeruginosa, Acinetobacter baumannii, carbapenemase-producing Enterobacteraciae and extended-spectrum β-lactamase producing bacteria. Proper management includes selecting appropriate antibiotics, optimizing dosing and using timely de-escalation based on antiimicrobial sensitivity data. Evidence-based strategies to prevent VAP that incorporate multidisciplinary staff education and collaboration are essential to reduce the burden of this disease and associated healthcare costs.

Ianthelliformisamines A-C, antibacterial bromotyrosine-derived metabolites from the marine sponge Suberea ianthelliformis

A high-throughput screening campaign using a prefractionated natural product library and an in vitro Pseudomonas aeruginosa (PAO200 strain) assay identified two antibacterial fractions derived from the marine sponge Suberea ianthelliformis. Mass-directed isolation of the CH(2)Cl(2)/CH(3)OH extract from S. ianthelliformis resulted in the purification of three new bromotyrosine-derived metabolites, ianthelliformisamines A-C (1-3), together with the known natural products aplysamine 1 (4) and araplysillin I (5). The structures of 1-3 were determined following analysis of 1D and 2D NMR and MS spectroscopic data. This is the first report of chemistry from the marine sponge S. ianthelliformis. Ianthelliformisamine A (1) showed inhibitory activity against the Gram-negative bacterium P. aeruginosa with an IC(50) value of 6.8 μM (MIC = 35 μM).

Pyrosequencing reveals the complex polymicrobial nature of invasive pyogenic infections: microbial constituents of empyema, liver abscess, and intracerebral abscess

The polymicrobial nature of invasive pyogenic infections may be underestimated by routine culture practices, due to the fastidious nature of many organisms and the loss of viability during transport or from prior antibacterials. Pyrosequencing was performed on brain and liver abscesses and pleural fluid and compared to routine culture data. Forty-seven invasive pyogenic infection samples from 44 patients [6 intracerebral abscess (ICA), 21 pyogenic liver abscess (PLA), and 18 pleural fluid (PF) samples] were assayed. Pyrosequencing identified an etiologic microorganism in 100 % of samples versus 45 % by culture, p <0.01. Pyrosequencing was also more likely than traditional cultures to classify infections as polymicrobial, 91 % versus 17 %, p <0.001. The median number of genera identified by pyrosequencing compared to culture was 1 [interquartile range (IQR) 1-3] versus 0 (IQR 0-1) for ICA, 7 (IQR 1-15) versus 1 (IQR 0-1) for PLA, and 15 (IQR 9-19) versus 0 (IQR 0-1) for PF. Where organisms were cultured, they typically represented the numerically dominant species identified by pyrosequencing. Complex microbial communities are involved in invasive pyogenic infection of the lung, liver, and brain. Defining the polymicrobial nature of invasive pyogenic infections is the first step towards appreciating the clinical and diagnostic implications of these complex communities.

Trends of Antibiotic Resistance in Mesophilic and Psychrotrophic Bacterial Populations during Cold Storage of Raw Milk

Psychrotrophic bacteria in raw milk are most well known for their spoilage potential and cause significant economic losses in the dairy industry. Despite their ability to produce several exoenzyme types at low temperatures, psychrotrophs that dominate the microflora at the time of spoilage are generally considered benign bacteria. It was recently reported that raw milk-spoiling Gram-negative-psychrotrophs frequently carried antibiotic resistance (AR) features. The present study evaluated AR to four antibiotics (ABs) (gentamicin, ceftazidime, levofloxacin, and trimethoprim-sulfamethoxazole) in mesophilic and psychrotrophic bacterial populations recovered from 18 raw milk samples, after four days storage at 4°C or 6°C. Robust analysis of variance and non parametric statistics (e.g., REGW and NPS) revealed that AR prevalence among psychrotrophs, for milk samples stored at 4°C, often equalled the initial levels and equalled or increased during the cold storage at 6°C, depending on the AB. The study performed at 4°C with an intermediate sampling point at day 2 suggested that (1) different psychrotrophic communities with varying AR levels dominate over time and (2) that AR (determined from relative amounts) was most prevalent, transiently, after 2-day storage in psychrotrophic or mesophilic populations, most importantly at a stage where total counts were below or around 10(5) CFU/mL, at levels at which the milk is acceptable for industrial dairy industrial processes.

Alkaloids from the Chinese vine Gnetum montanum

During a high-throughput screening campaign of a prefractionated natural product library, fractions from the Chinese vine Gnetum montanum showed in vitro activity against Pseudomonas aeruginosa wild-type strain, PAO1. UV-directed isolation of the organic extract from the vine leaves resulted in the purification of the new natural products N-methyllaudanosolinium trifluoroacetate (1), 3'-hydroxy-N,N-dimethylcoclaurinium trifluoroacetate (2), 1,9,10-trihydroxy-2-methoxy-6-methylaporphinium trifluoroacetate (3), and 6a,7-didehydro-1,9,10-trihydroxy-2-methoxy-6-methylaporphinium trifluoroacetate (4). Compound 4 is described here for the first time, and this is the first report of compounds 1-3 as natural products. Compounds 1-3 were found to racemize over time. Starting from commercially available (+)-boldine, through a series of semisynthetic reactions, a mechanism for the racemization of the isolated compounds is proposed. The known natural products (-)-latifolian A (5) and magnocurarine (6) were also isolated during these studies. The antibacterial activity was explained by the presence of 5, which displayed an IC50 value of 9.8 μM (MIC = 35 μM).

Development and application of a cellular, gain-of-signal, bioluminescent reporter screen for inhibitors of type II secretion in Pseudomonas aeruginosa and Burkholderia pseudomallei

The type II secretion (T2S) system in gram-negative bacteria comprises the Sec and Tat pathways for translocating proteins into the periplasm and an outer membrane secretin for transporting proteins into the extracellular space. To discover Sec/Tat/T2S pathway inhibitors as potential new therapeutics, the authors used a Pseudomonas aeruginosa bioluminescent reporter strain responsive to SecA depletion and inhibition to screen compound libraries and characterize the hits. The reporter strain placed a luxCDABE operon under regulation of a SecA depletion-responsive upregulated promoter in a secA deletion background complemented with an ectopic lac-regulated secA copy. Bioluminescence was indirectly proportional to the isopropyl-β-D-thiogalactopyranoside concentration and stimulated by azide, a known SecA ATPase inhibitor. A total of 96 compounds (0.1% of 73,000) were detected as primary hits due to stimulation of luminescence with a z score ≥5. Direct secretion assays of the nine most potent hits, representing five chemical scaffolds, revealed that they do not inhibit SecA-mediated secretion of β-lactamase into the periplasm but do inhibit T2S-mediated extracellular secretion of elastase with IC(50) values from 5 to 25 µM. In addition, seven of the nine compounds also inhibited the T2S-mediated extracellular secretion of phospholipase C by P. aeruginosa and protease activity by Burkholderia pseudomallei.

Akt-mediated proinflammatory response of mononuclear phagocytes infected with Burkholderia cenocepacia occurs by a novel GSK3β-dependent, IκB kinase-independent mechanism

The environmental bacterium Burkholderia cenocepacia causes opportunistic lung infections in immunocompromised individuals, particularly in patients with cystic fibrosis. Infections in these patients are associated with exacerbated inflammation leading to rapid decay of lung function, and in some cases resulting in cepacia syndrome, which is characterized by a fatal acute necrotizing pneumonia and sepsis. B. cenocepacia can survive intracellularly in macrophages by altering the maturation of the phagosome, but very little is known on macrophage responses to the intracellular infection. In this study, we have examined the role of the PI3K/Akt signaling pathway in B. cenocepacia-infected monocytes and macrophages. We show that PI3K/Akt activity was required for NF-κB activity and the secretion of proinflammatory cytokines during infection with B. cenocepacia. In contrast to previous observations in epithelial cells infected with other Gram-negative bacteria, Akt did not enhance IκB kinase or NF-κB p65 phosphorylation, but rather inhibited GSK3β, a negative regulator of NF-κB transcriptional activity. This novel mechanism of modulation of NF-κB activity may provide a unique therapeutic target for controlling excessive inflammation upon B. cenocepacia infection.

Efflux pump inhibitors (EPIs) as new antimicrobial agents against Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic human pathogen and one of the leading causes of nosocomial infections worldwide. The difficulty in treatment of pseudomonas infections arises from being multidrug resistant (MDR) and exhibits resistance to most antimicrobial agents due to the expression of different mechanisms overcoming their effects. Of these resistance mechanisms, the active efflux pumps in Pseudomonas aeruginosa that belong to the resistance nodulation division (RND) plays a very important role in extruding the antibiotics outside the bacterial cells providing a protective means against their antibacterial activity. Beside its role against the antimicrobial agents, these pumps can extrude biocides, detergents, and other metabolic inhibitors. It is clear that efflux pumps can be targets for new antimicrobial agents. Peptidomimetic compounds such as phenylalanine arginyl β-naphthylamide (PAβN) have been introduced as efflux pump inhibitors (EPIs); their mechanism of action is through competitive inhibition with antibiotics on the efflux pump resulting in increased intracellular concentration of antibiotic, hence, restoring its antibacterial activity. The advantage of EPIs is the difficulty to develop bacterial resistance against them, but the disadvantage is their toxic property hindering their clinical application. The structure activity relationship of these compounds showed other derivatives from PAβN that are higher in their activity with higher solubility in biological fluids and decreased toxicity level. This raises further questions on how can we compact Pseudomonas infections. Of particular importance, the recent resurgence in the use of older antibiotics such as polymyxins and probably applying stricter control measures in order to prevent their spread in clinical sittings.

A two-tier model of polymyxin B resistance in Burkholderia cenocepacia

Burkholderia cenocepacia is an environmental bacterium causing serious human opportunistic infections and is extremely resistant to multiple antibiotics including antimicrobial peptides, such as polymyxin B (PmB). Extreme antibiotic resistance is attributed to outer membrane impermeability ('intrinsic' resistance). Previous work showed that production of full-length lipopolysaccharide (LPS) prevents surface binding of PmB. We hypothesized that two tiers of resistance mechanisms rendering different thresholds of PmB resistance exist in B. cenocepacia. To test this notion, candidate genes were mutated in two isogenic strains expressing full-length LPS or truncated LPS devoid of heptose ('heptoseless LPS') respectively. We uncovered various proteins required for PmB resistance only in the strain with heptoseless LPS. These proteins are not involved in preventing PmB binding to whole cells or permeabilization of the outer membrane. Our results support a two-tier model of PmB resistance in B. cenocepacia. One tier sets a very high threshold mediated by the LPS and the outer membrane permeability barrier. The second tier sets a lower threshold that may play a role in PmB resistance only when outer membrane permeability is compromised. This model may be of general applicability to understanding the high antimicrobial peptide resistance of environmental opportunistic pathogens.