Clinical epidemiology and resistance mechanisms of carbapenem-resistant Acinetobacter baumannii, French Guiana, 2008-2014

A Review of Resistance to Polymyxins and Evolving Mobile Colistin Resistance Gene (mcr) among Pathogens of Clinical Significance

The global rise in antibiotic resistance in bacteria poses a major challenge in treating infectious diseases. Polymyxins (e.g., polymyxin B and colistin) are last-resort antibiotics against resistant Gram-negative bacteria, but the effectiveness of polymyxins is decreasing due to widespread resistance among clinical isolates. The aim of this literature review was to decipher the evolving mechanisms of resistance to polymyxins among pathogens of clinical significance. We deciphered the molecular determinants of polymyxin resistance, including distinct intrinsic molecular pathways of resistance as well as evolutionary characteristics of mobile colistin resistance. Among clinical isolates, Acinetobacter stains represent a diversified evolution of resistance, with distinct molecular mechanisms of intrinsic resistance including naxD, lpxACD, and stkR gene deletion. On the other hand, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa are usually resistant via the PhoP-PhoQ and PmrA-PmrB pathways. Molecular evolutionary analysis of mcr genes was undertaken to show relative relatedness across the ten main lineages. Understanding the molecular determinants of resistance to polymyxins may help develop suitable and effective methods for detecting polymyxin resistance determinants and the development of novel antimicrobial molecules.

CRISPR-Based Gene Editing in Acinetobacter baumannii to Combat Antimicrobial Resistance

Antimicrobial resistance (AMR) poses a significant threat to the health, social, environment, and economic sectors on a global scale and requires serious attention to addressing this issue. Acinetobacter baumannii was given top priority among infectious bacteria because of its extensive resistance to nearly all antibiotic classes and treatment options. Carbapenem-resistant A. baumannii is classified as one of the critical-priority pathogens on the World Health Organization (WHO) priority list of antibiotic-resistant bacteria for effective drug development. Although available genetic manipulation approaches are successful in A. baumannii laboratory strains, they are limited when employed on newly acquired clinical strains since such strains have higher levels of AMR than those used to select them for genetic manipulation. Recently, the CRISPR-Cas (Clustered regularly interspaced short palindromic repeats/CRISPR-associated protein) system has emerged as one of the most effective, efficient, and precise methods of genome editing and offers target-specific gene editing of AMR genes in a specific bacterial strain. CRISPR-based genome editing has been successfully applied in various bacterial strains to combat AMR; however, this strategy has not yet been extensively explored in A. baumannii. This review provides detailed insight into the progress, current scenario, and future potential of CRISPR-Cas usage for AMR-related gene manipulation in A. baumannii.

Burden of severe infections due to carbapenem-resistant pathogens in intensive care unit

Intensive care units (ICU) for various reasons, including the increasing age of admitted patients, comorbidities, and increasingly complex surgical procedures (e.g., transplants), have become "the epicenter" of nosocomial infections, these are characterized by the presence of multidrug-resistant organisms (MDROs) as the cause of infection. Therefore, the perfect match of fragile patients and MDROs, as the cause of infection, makes ICU mortality very high. Furthermore, carbapenems were considered for years as last-resort antibiotics for the treatment of infections caused by MDROs; unfortunately, nowadays carbapenem resistance, mainly among Gram-negative pathogens, is a matter of the highest concern for worldwide public health. This comprehensive review aims to outline the problem from the intensivist's perspective, focusing on the new definition and epidemiology of the most common carbapenem-resistant MDROs (Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacterales) to emphasize the importance of the problem that must be permeating clinicians dealing with these diseases.

Carbapenem-resistant Acinetobacter baumannii: A challenge in the intensive care unit

Carbapenem-resistant Acinetobacter baumannii (CRAB) has become one of the leading causes of healthcare-associated infections globally, particularly in intensive care units (ICUs). Cross-transmission of microorganisms between patients and the hospital environment may play a crucial role in ICU-acquired CRAB colonization and infection. The control and treatment of CRAB infection in ICUs have been recognized as a global challenge because of its multiple-drug resistance. The main concern is that CRAB infections can be disastrous for ICU patients if currently existing limited therapeutic alternatives fail in the future. Therefore, the colonization, infection, transmission, and resistance mechanisms of CRAB in ICUs need to be systematically studied. To provide a basis for prevention and control countermeasures for CRAB infection in ICUs, we present an overview of research on CRAB in ICUs, summarize clinical infections and environmental reservoirs, discuss the drug resistance mechanism and homology of CRAB in ICUs, and evaluate contemporary treatment and control strategies.

Resistance traits and molecular characterization of multidrug-resistant Acinetobacter baumannii isolates from an intensive care unit of a tertiary hospital in Guangdong, southern China

PURPOSE

This study aims to characterize antimicrobial resistance (AMR) of all the non-duplicated Acinetobacter baumannii strains isolated from an intensive care unit in a tertiary hospital during the period of January 1 to December 31, 2015.

METHODS

A. baumannii (n = 95 strains) isolated from patients was subjected to antimicrobial susceptibility test (AST) by Vitek 2 Compact system to determine minimum inhibitory concentrations, followed by genotyping by enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR). Resistance genes of interest were PCR amplified and sequenced.

RESULTS

All isolates were qualified as MDR, with a resistance rate of > 80% to 8 antimicrobials tested. In terms of beta-lactamase detection, the bla_OXA23, bla_TEM-1, and armA genes were detected frequently at 92.63%, 9 1.58%, and 88.42%, respectively. The metallo-β-lactamase genes bla_IMP and bla_VIM were undetected. Aph (3')-I was detected in 82 isolates (86.32%), making it the most prevalent aminoglycoside-modifying enzyme (AMEs) encoding gene. In addition, ant (3″)-I was detected at 30.53%, while 26.32% of the strains harbored an aac (6')-Ib gene. ERIC-PCR typing suggested moderate genetic diversity among the isolates, which might be organized into 10 distinct clusters, with cluster A (n = 86 isolates or 90.53%) being the dominant cluster.

CONCLUSIONS

All of the A. baumannii strains detected in the ICU were MDR clones exhibiting extremely high resistance to carbapenems and aminoglycosides as monitored throughout the study period. They principally belonged to a single cluster of isolates carrying bla_OXA23 and armA co-producing different AMEs genes.

Acinetobacter baumannii: insights towards a comprehensive approach for the prevention of outbreaks in health-care facilities

Acinetobacter baumannii is known to be an opportunistic pathogen frequently responsible for outbreaks in health-care facilities, particularly in Intensive Care Units (ICU). It can easily survive in the hospital setting for long periods and can be transmitted throughout the hospital in a variety of ways, explored in this review. It can also easily acquire antibiotic resistance determinants rendering several antibiotic drugs useless. In 2019, the US Centre for Disease Control (CDC) considered the organism as an urgent threat. The aim of this review was to raise the awareness of the medical community about the relevance of this pathogen and discuss how it may impact seriously the healthcare institutions particularly in the aftermath of the recent COVID-19 pandemic. PubMed was searched, and articles that met inclusion criteria were reviewed. We conclude by the need to raise awareness to this pathogen's relevance and to encourage the implementation of preventive measures in order to mitigate its consequences namely the triage of specific high-risk patients.

Correlative proteomics identify the key roles of stress tolerance strategies in Acinetobacter baumannii in response to polymyxin and human macrophages

The opportunistic pathogen Acinetobacter baumannii possesses stress tolerance strategies against host innate immunity and antibiotic killing. However, how the host-pathogen-antibiotic interaction affects the overall molecular regulation of bacterial pathogenesis and host response remains unexplored. Here, we simultaneously investigate proteomic changes in A. baumannii and macrophages following infection in the absence or presence of the polymyxins. We discover that macrophages and polymyxins exhibit complementary effects to disarm several stress tolerance and survival strategies in A. baumannii, including oxidative stress resistance, copper tolerance, bacterial iron acquisition and stringent response regulation systems. Using the spoT mutant strains, we demonstrate that bacterial cells with defects in stringent response exhibit enhanced susceptibility to polymyxin killing and reduced survival in infected mice, compared to the wild-type strain. Together, our findings highlight that better understanding of host-pathogen-antibiotic interplay is critical for optimization of antibiotic use in patients and the discovery of new antimicrobial strategy to tackle multidrug-resistant bacterial infections.

Epidemiological and genomic characteristics of Acinetobacter baumannii from different infection sites using comparative genomics

Background

Acinetobacter baumannii is a common nosocomial pathogen that poses a huge threat to global health. Owing to the severity of A. baumannii infections, it became necessary to investigate the epidemiological characteristics of A. baumannii in Chinese hospitals and find the reasons for the high antibiotic resistance rate and mortality. This study aimed to investigate the epidemiologic and genetic characteristics of A. baumannii isolated from patients with hospital acquired pneumonia (HAP), bloodstream infection (BSI) and urinary tract infection (UTI) in China and uncover potential mechanisms for multi-drug resistance and virulence characteristics of A. baumannii isolates.

Results

All isolates were classified into two primary clades in core gene-based phylogenetic relationship. Clonal complex 208 (CC208) mainly consisted of ST195 (32 %) and ST208 (24.6 %). CC208 and non-CC208 isolates had carbapenem resistance rates of 96.2 and 9.1 %, respectively. Core genes were enriched in ‘Amino acid transport and metabolism’, ‘Translation’, ‘Energy production and conversion’, ‘Transcription’, ‘Inorganic ion transport and metabolism’ and ‘Cell wall/membrane/envelope synthesis’. Most isolates possessed virulence factors related to polysaccharide biosynthesis, capsular polysaccharide synthesis and motility. Eleven isolates belong to ST369 or ST191 (oxford scheme) all had the virulence factor cap8E and it had a higher positive rate in UTI (35.3 %) than in BSI (18.9 %) and HAP (12.9 %). ABGRI1 antibiotic resistance islands were responsible for streptomycin, tetracycline and sulfonate resistance. The bla_OXA−23 gene was the most probable cause for carbapenem resistance, although the bla_OXA−66 gene with nonsynonymous SNPs (F82L, I129L) was not.

Conclusions

A. baumannii is a genomically variable pathogen that has the potential to cause a range of infectious diseases. There is high proportion of carbapenem resistance in isolates from all three infection sites (HAP, BSI and UTI), which can be attributed to the bla_OXA−23 gene. CC208 is the predominant clone in bla_OXA−23-carrying A. baumannii that should be monitored. Virulence factors involving bacteria motility and polysaccharide biosynthesis which are widespread in clinical A. baumannii strains deserve our attention.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07842-5.

Carbapenem resistance in Acinetobacter baumannii, and their importance in hospital-acquired infections: a scientific review

Carbapenem is an important therapy for serious hospital-acquired infections and for the care of patients affected by multidrug-resistant organisms, specifically Acinetobacter baumannii; however, with the global increase of carbapenem-resistant A. baumannii, this pathogen has significantly threatened public health. Thus, there is a pressing need to better understand this pathogen in order to develop novel treatments and control strategies for dealing with A. baumannii. In this review, we discuss an overview of carbapenem, including its discovery, development, classification and biological characteristics, and its importance in hospital medicine especially in critical care units. We also describe the peculiarity of bacterial pathogen, A. baumannii, including its commonly reported virulence factors, environmental persistence and carbapenem resistance mechanisms. In closing, we discuss various control strategies for overcoming carbapenem resistance in hospitals and for limiting outbreaks. With the appearance of strains that resist carbapenem, the aim of this review is to highlight the importance of understanding this increasingly problematic healthcare-associated pathogen that creates significant concern in the field of nosocomial infections and overall public health.

The distribution of mutations and hotspots in transcription regulators of resistance-nodulation-cell division efflux pumps in tigecycline non-susceptible Acinetobacter baumannii in China

OBJECTIVE

Acinetobacter baumannii has emerged as a problematic hospital pathogen and tigecycline is among the few remaining antibiotics retaining activity against multidrug-resistant A. baumannii. This study was aimed to elucidate the tigecycline resistance mechanisms in 28 unique clinical A. baumannii strains from nine provinces in China.

METHODS

Whole genome sequences were obtained via Illumina HiSeq sequencing and regulatory genes of efflux pumps were analyzed. Minimal inhibitory concentrations (MICs) were determined by agar/microbroth dilution according to the guidelines recommended by Clinical and Laboratory Standards Institute (CLSI). Tigecycline susceptibility data was interpreted using breakpoints for Enterobacterales recommended by EUCAST v8.1.

RESULTS

The majority of isolates belonged to the international clonal lineage IC2 (n = 27, 96.4%). Four isolates were considered tigecycline-intermediate (MIC = 2 mg/L), twenty-four isolates were tigecycline-resistant. The insertion of ISAba1 in adeS was found in six isolates and was the most prevalent insertion element (IS). In four isolates we observed an insertion of ISAba1 in adeN, and two of them had IS26 insertions. Two mutations in adeN (deletion and premature stop codon) were observed only in the MIC = 4 mg/L isolates. Other mutations in adeRS (amino acid insertion/substitutions and premature stop codons) were only detected in the MIC ≥ 8 group. The novel substitutions E219 K in adeR and A130 T in adeS were observed in five and four isolates respectively, suggesting a mutational hotspot.

CONCLUSIONS

This study demonstrates that changes in transcription regulators were important mechanisms in tigecycline resistance in A. baumannii. Also, we identified several chromosomal hotspots that can be used for prediction of tigecycline resistance.

Update on the epidemiology of carbapenemases in Latin America and the Caribbean

INTRODUCTION

Carbapenemases are β-lactamases able to hydrolyze a wide range of β-lactam antibiotics, including carbapenems. Carbapenemase production in Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter spp., with and without the co-expression of other β-lactamases is a serious public health threat. Carbapenemases belong to three main classes according to the Ambler classification: class A, class B, and class D.

AREAS COVERED

Carbapenemase-bearing pathogens are endemic in Latin America. In this review, we update the status of carbapenemases in Latin America and the Caribbean.

EXPERT OPINION

Understanding the current epidemiology of carbapenemases in Latin America and the Caribbean is of critical importance to improve infection control policies limiting the dissemination of multi-drug-resistant pathogens and in implementing appropriate antimicrobial therapy.

From food to hospital: we need to talk about Acinetobacter spp

Some species of the genus Acinetobacter are admittedly important hospital pathogens. Additionally, various animal and plant foods have been linked to the presence of Acinetobacter, including resistant strains. However, due to isolation difficulties and the lack of official standard methods, there is a dearth of work and epidemiological data on foodborne diseases caused by this microorganism. Considering that Acinetobacter spp. may represent a serious public health problem, especially because of their resistance to carbapenems and colistin, and because of the fact that these pathogens may transfer resistance genes to other bacteria, studies are needed to evaluate the pathogenicity of both food and clinical isolates and to search for them using control strategies, such as the adoption of more efficient disinfection measures and use of antimicrobial substances (AMS). In contrast, AMS production by strains of the genus Acinetobacter has already been described, and its potential for application against other Gram-negative food or clinical pathogens, reveals a new field to be explored.

Dissemination of blaOXA-23-harbouring carbapenem-resistant Acinetobacter baumannii clones in Pakistan

OBJECTIVES

The rise of carbapenem resistance in Acinetobacter baumannii represents a challenge for the therapeutic management of infections. The present study aimed to investigate the sequence types (STs) and carbapenem resistance in A. baumannii strains collected from various clinical specimens from patients admitted to five tertiary-care hospitals in Pakistan.

METHODS

A total of 156 A. baumannii clinical strains were analysed for antimicrobial susceptibility, followed by genetic screening for carbapenem resistance determinants. All of the strains were typed by multilocus sequence typing (MLST) according to the Pasteur scheme.

RESULTS

Of the 156 A. baumannii isolates, 139 (89.1%) were carbapenem-resistant, of which 136 carried bla_OXA-23-like genes. Interestingly, the most commonly identified ST was ST589 (n = 52), classified as clonal complex 1 (CC1). ST2 was the second most common (n = 38), corresponding to CC2/92 (Pasteur/Oxford scheme), which was distributed in all five hospitals.

CONCLUSION

Diverse clones of carbapenem-resistant A. baumannii, including previously reported STs as well as new STs, carrying bla_OXA-23 are distributed in Pakistan. This is the first study to describe the molecular epidemiology of widely disseminated A. baumannii isolates in Pakistan. The findings will help to improve our knowledge of the predominant STs and will be valuable for a deeper understanding of resistance mechanisms among various STs.

In vitro interactions of ambroxol hydrochloride or amlodipine in combination with antibacterial agents against carbapenem-resistant Acinetobacter baumannii

The aim of this study was to investigate the in vitro interactions of ambroxol hydrochloride (ABH) or amlodipine (AML) with commonly used antibacterial agents, including meropenem, imipenem-cilastatin sodium, biapenem, cefoperazone-sulbactam, polymyxin B, and tigecycline, against six carbapenem-resistant Acinetobacter baumannii (CRAB) clinical isolates. Drug interactions were interpreted using two models, that is, the fractional inhibitory concentration index (FICI) model and the percentage of growth difference (ΔE) model. The results show that a majority of the combination groups exhibited partial synergy and additive interactions, such as the combinations of carbapenems and cefoperazone-sulbactam (SCF) with ABH or AML. While the combination of PB/AML exhibited synergistic interactions against all tested isolates, and PB/ABH exhibited synergistic interactions against two isolates. The FICI and ΔE model correlated very well for the combinations of PBABH and PB/AML against AB2. The combinations of TGC with ABH or AML mainly exhibited additive and indifferent interactions. There were no antagonistic interactions observed in any of the combinations. In conclusion, this study revealed that the non-antibacterial agents ABH or AML can work synergistically or partial synergistically with antibacterial agents against CRAB. This finding is crucial for overcoming the carbapenem resistance of A. baumannii. SIGNIFICANCE AND IMPACT OF THE STUDY: Drug combination is an effective approach for the treatment of resistant bacterial infection. The significance of using drug combination is that it can reduce drug dosage requirements, reduce the toxic effects of agents and prevent or delay the emergence of drug resistance. This study measured the in vitro interactions between non-antimicrobial agents and antibacterial agents against carbapenem-resistant Acinetobacter baumannii and the results of this study provide new insight to find strategies to overcome the carbapenem resistance in A. baumannii.

Global prevalence of colistin resistance in clinical isolates of Acinetobacter baumannii: A systematic review and meta-analysis

INTRODUCTION

Acinetobacter baumannii antimicrobial resistance is a public health concern in developing and developed countries, especially in the hospital setting. Understanding the antibiotic resistance profile can help to provide better guidelines for the prescription of appropriate antibiotics, reduction of antibiotic resistance, and introducing new and effective treatment options.

METHOD

Using the PRISMA guidelines, databases of PubMed, Embase, and Cochrane Library were searched systematically from January 1, 2000, to January 1, 2018. All statistical analyses were carried out via Comprehensive Meta-Analysis Software Version 2.0 (Biostat, Englewood, NJ). Depending on the heterogeneity test, either random or fix effect models were used for determining the pooled prevalence of drug resistance.

RESULT

A total of 150 studies were included from 41 countries of six different WHO regional offices worldwide. The highest and the lowest rate of resistance were observed for cefotaxime (99%, 95% CI: 95-99.9) in Africa and colistin (1.1%, 95% CI: 0.3-4.5) in Western Pacific, respectively. Lebanon (17.5%, 95% CI: 16-19) and China (12%, 95% CI: 3.5-32.5) had the highest and Germany (0.2%, 95% CI: 0-2.5) had the lowest rate of resistance for colistin.

CONCLUSION

Our analysis showed that prevalence and rate of increased colistin resistance in South-East Asia and Eastern Mediterranean countries are higher than other regions of the world. Therefore, the establishment of appropriate antibiotic usage guidelines should be essential in these countries.

Pharmacokinetic and pharmacodynamic profiling of four antimicrobials against Acinetobacter baumannii infection

BACKGROUND

The aim of this study was to evaluate common antimicrobial regimens used in eradicating Acinetobacter baumannii in Shenyang, China.

METHODS

Monte Carlo simulation was conducted to estimate the probability target attainment (PTA) and cumulative fraction of response (CFR) for imipenem, cefoperazone/sulbactam (2:1), tigecycline and colistin methanesulfonate.

RESULTS

For the results of PTAs, imipenem following administration of 0.5 g q6 h, 1 g q8 h, and 1 g q6 h for both 0.5 h and 2 h infusion achieved＞90% PTAs when MIC was 8 μg/ml; cefoperazone/ sulbactam (2:1) following administration of 4.5 g q6 h and 6 g q6 h achieved＞90% PTAs when MIC was 64μg/ml; tigecycline following administration of 50 mg q12 h and 100 mg q12 h achieved＞90% PTAs when MIC was 1 μg/ml; colistin methanesulfonate with high dosages (3MU q8 h) could provide high PTA (95.13%) in patients with CL_Cr＜60 ml/min when MIC was 2 μg/ml. As for CFR values of four antibiotics, imipenem achieved the lowest CFR values. For cefoperazone/sulbactam (2:1) and tigecycline, with simulated regimens improvement, the CFR values were both increased, and there were obviously increasing CFR values against Acinetobacter baumannii. For colistin methanesulfonate, the most aggressive dosage of 3MU q8 h could provide satisfactory CFR values (≥86.94%) against Acinetobacter baumannii in patients at various CL_Cr.

CONCLUSION

This study suggested that measurement of MICs, individualized therapy and therapeutic drug-level monitoring should be considered together to achieve the optimal drug exposure. That will provide the best chance of achieving the highest probability of a successful clinical or microbiological response, and avoiding the induced resistance.

Predictors of mortality in patients infected with carbapenem-resistant Acinetobacter baumannii: A systematic review and meta-analysis

BACKGROUND

Carbapenem-resistant Acinetobacter baumannii (CRAB) tops the list of threats to human health. Studies exploring predictors of mortality in patients with CRAB infection produced conflicting results.

METHODS

A systematic search of the PubMed, Embase, and the Cochrane Library databases was performed from inception to June 2018 to identify studies reporting mortality predictors in patients infected with CRAB. Two authors independently assessed trials for inclusion and data extraction.

RESULTS

A total of 19 observational studies were enrolled in this study. Factors associated with mortality of patients infected with CRAB were inappropriate empirical antimicrobial treatment (odds ratio [OR], 5.04; 95% confidence interval [CI], 2.56-9.94), septic shock (OR, 5.65; 95% CI, 2.35-13.57), chronic liver disease (OR, 2.36; 95% CI, 1.33-4.16), chronic renal disease (OR, 2.02; 95% CI, 1.37-2.99), hypertension (OR, 1.74; 95% CI, 1.08-2.80), neutropenia (OR, 3.31; 95% CI, 1.25-8.77), immunosuppressant use (OR, 3.15; 95% CI, 1.94-5.11), total parenteral nutrition (OR, 1.66; 95% CI, 1.08-2.56), and intubation (OR, 5.03; 95% CI, 2.33-10.87). Acute Physiology and Chronic Health Evaluation II score at admission and Pitt bacteremia score at the onset of CRAB bacteremia were higher in nonsurvivors.

CONCLUSIONS

Our study suggests that severity of baseline condition and receiving inappropriate experience antibiotic therapy are major risk factors for higher mortality in patients with CRAB infections. These findings may help clinicians to take appropriate preventive measures and decrease mortality in such patients.

Emergent Polymyxin Resistance: End of an Era?

Until recently, the polymyxin antibiotics were used sparingly due to dose limiting toxicities. However, the lack of therapeutic alternatives for infections caused by highly resistant Gram-negative bacteria has led to the increased use of the polymyxins. Unfortunately, the world has witnessed increased rates of polymyxin resistance in the last decade, which is likely in part due to its irrational use in human and veterinary medicine. The spread of polymyxin resistance has been aided by the dissemination of the transferable polymyxin-resistance gene, mcr, in humans and the environment. The mortality of colistin-resistant bacteria (CoRB) infections varies in different reports. However, poor clinical outcome was associated with prior colistin treatment, illness severity, complications, and multidrug resistance. Detection of polymyxin resistance in the clinic is possible through multiple robust and practical tests, including broth microdilution susceptibility testing, chromogenic agar testing, and molecular biology assays. There are multiple risk factors that increase a person’s risk for infection with a polymyxin-resistant bacteria, including age, prior colistin treatment, hospitalization, and ventilator support. For patients that are determined to be infected by polymyxin-resistant bacteria, various antibiotic treatment options currently exist. The rising trend of polymyxin resistance threatens patient care and warrants effective control.

Temporal evolution of Acinetobacter baumannii ST107 clone: conversion of blaOXA-143 into blaOXA-231 coupled with mobilization of ISAba1 upstream occAB1

Nine carbapenem-resistant Acinetobacter baumannii isolates carrying bla_OXA-231 and an ISAba1 upstream occAB1 were evaluated. They were clonally related and belonged to ST107. An OXA-143-producing A. baumannii ST107 strain (Ac-148) that did not possess ISAba1 upstream occAB1 was included in the analysis. Reduction in the expression of occAB1 and a 4-fold increase of carbapenem MICs were observed for all isolates, except for the Ac-148 strain, probably due to the presence of ISAba1 upstream occAB1 but in the same transcriptional orientation. We reported an A. baumannii ST107 clone carrying bla_OXA-143 that acquired a mutation resulting into bla_OXA-231 and mobilized ISAba1 upstream occAB1.

Analysis of global prevalence of antibiotic resistance in Acinetobacter baumannii infections disclosed a faster increase in OECD countries

Acinetobacter baumannii is one of the most challenging nosocomial pathogens due to the emergence and widespread of antibiotic resistance. We aimed to provide the first analysis of global prevalence of antibiotic resistance in A. baumannii infections, by synthesizing data and knowledge through a systematic review. We searched studies reporting antibiotic resistance in A. baumannii infections using the Medline, Embase, Web of Science, and Cochrane databases from January 2000 to December 2016. Studies were eligible if they investigated and reported antibiotic resistance in A. baumannii infections with inpatients or outpatients in hospital. Our investigation showed a high prevalence of resistance to the common prescribed antibiotics in A. baumannii infections in both OECD (Organization for Economic Co-operation and Development) and non-OECD countries. Strikingly, though OECD countries have substantially lower pooled prevalence of resistance compared to non-OECD countries based on the data during 2006-2016, a further investigation in a time scale disclosed a faster increase in OECD countries during the past 11 years, and currently both of them have a comparable prevalence of resistance (2011-2016). Tigecycline and colistin are still active but their resistances are expected to become common if the preventative measures are not taken. Antibiotic resistance in A. baumannii infection developed fast and is a crisis for both OECD and non-OECD countries. A "post-antibiotic era" for A. baumannii infection is expected in the next 10-20 years without immediate actions from pharmaceutical companies and governments.

Draft genome sequence of a multidrug-resistant OXA-23-producing Acinetobacter baumannii ST191 clinical isolate from China

Acinetobacter baumannii has emerged worldwide as a dominant pathogen in nosocomial infections. In this study, we report the draft genome sequence of a clinical multidrug-resistant (MDR) A. baumannii ST191 (CC92) strain. Whole-genome sequencing of the isolate was performed using an Illumina HiSeq™ 2500 system, and bioinformatics analysis was also performed. The draft genome length was 4,259,210bp, harbouring 14 gene sequences relevant to antibiotic resistance. Antimicrobial susceptibility testing revealed that the isolate was resistant to all of the tested antibiotics except for tigecycline and colistin. These data will facilitate further understanding of the genomic and resistance features of MDR A. baumannii.

Emergence of the Uncommon Clone ST944/ST78 Carrying blaOXA-40-like and blaCTX-M-like Genes Among Carbapenem-Nonsusceptible Acinetobacter baumannii in Moscow, Russia

Carbapenem-nonsusceptible (Carba-NS) Acinetobacter baumannii has emerged as an important cause of nosocomial infections. In the present study, we characterized 91 Carba-NS A. baumannii isolates collected from patients of surgical departments and intensive care units at three hospitals in Moscow in 2012-2015. Multilocus sequence typing (MLST) using the Oxford (Oxf) scheme identified 16 sequence types (STs) of three clonal complexes (CCs), including CC92^Oxf (67%), CC109^Oxf (1%), CC944^Oxf (29%), and the singleton ST1100^Oxf (3%). CC944^Oxf was composed of ST944^Oxf (n = 16) and two of its newly described single locus variants ST1103^Oxf (n = 3) and ST1104^Oxf (n = 7); all the three STs were identical to the Pasteur (Pas) MLST scheme ST78. All CC944^Oxf/ST78^Pas isolates were bla_OXA-40-like positive and all but one isolate harbored a bla_CTX-M-like gene. ST944^Oxf was the only ST found in each of the three study hospitals. Biofilm growth capacity was similar among Carba-NS and nonclonal carbapenem-susceptible isolates. Our data demonstrate the predominance of two clonal lineages among Carba-NS A. baumannii. One of these, the uncommon bla_OXA-40-like/bla_CTX-M-like-positive clone of CC944^Oxf/ST78^Pas, seems to be endemic in Russia.

Resistance to polymyxins in Gram-negative organisms

Polymyxins have recently been re-introduced into the therapeutic arsenal to combat infections caused by multidrug-resistant Gram-negative bacteria. However, the emergence of strains resistant to these last-resort drugs is becoming a critical issue in a growing number of countries. Both intrinsic and transferable mechanisms of polymyxin resistance have been characterised. These mechanisms as well as the epidemiological data regarding four relevant bacterial pathogens (Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii and Pseudomonas aeruginosa) are considered in this review. A special focus is made on plasmid-mediated resistance and the spread of mcr genes.