Spread Of Carbapenem-resistant Acinetobacter Baumannii Research Articles

Characteristics of the Genetic Spread of Carbapenem-Resistant Acinetobacter baumannii in a Tertiary Greek Hospital.

Acinetobacter baumannii (Ab) has increasingly been identified as a cause of hospital-acquired infections and epidemics. The rise of carbapenem-resistant Acinetobacter baumannii (CRAB) poses significant challenges in treatment. Nosocomial outbreaks linked to CRAΒ A. baumannii strains have been reported worldwide, including in Greece. This study aimed to analyze the molecular epidemiology trends of multidrug-resistant A. baumannii isolates in a tertiary hospital in Athens, Greece. A total of 43 clinical isolates of extensively drug-resistant (XDRAB), pan-drug-resistant (PDRAB), and CRAB were collected from patients suffering from blood infection, hospitalized between 2016 and 2020 at the internal medicine clinics and the ICU. A.baumannii isolates underwent testing for Ambler class B and D carbapenemases and the detection of ISAba1, and were typed, initially, using pulsed-field gel electrophoresis, and, subsequently, using sequence-based typing and multiplex PCR to determine European Clone lineages. The blaOXA-23 gene accompanied by ISAba1 was prevalent in nearly all A. baumannii isolates, except for one carrying blaOXA-58. The intrinsic blaOXA-51-like gene was found in all isolates. No Ambler class B carbapenemases (VIM, NDM) were detected. Isolates were grouped into four PF-clusters and no one-cluster spread was documented, consistent with the absence of outbreak. The study indicated that XDR/PDR-CRAB isolates predominantly produce OXA-23 carbapenemase and belong to European Clone II. Further research is needed to understand the distribution of resistant bacteria and develop effective prevention and control strategies.

Endemicity and diversification of carbapenem-resistant Acinetobacter baumannii in an intensive care unit

Carbapenem-resistant Acinetobacter baumannii (CRAB) is a major public health concern globally. Often studied in the context of hospital outbreaks, little is known about the persistence and evolutionary dynamics of endemic CRAB populations. A three-month cross-sectional observational study was conducted in a 28-bed intensive care unit (ICU) in Hangzhou, China. A total of 5068 samples were collected from the hospital environment (n=3985), patients (n=964) and staff (n=119). CRAB isolates were obtained from 10.5% of these samples (n=532). All of these isolates, plus an additional 19 from clinical infections, were characterised through whole-genome sequencing. The ICU CRAB population was dominated by OXA-23-producing global clone 2 isolates (99.3% of all isolates) that could be divided into 20 distinct clusters, defined through genome sequencing. CRAB was persistently present in the ICU, driven by regular introductions of distinct clusters. The hospital environment was heavily contaminated, with CRAB isolated from bed units on 183/335 (54.6%) sampling occasions but from patients on only 72/299 (24.1%) occasions. CRAB was spread to adjacent bed units and rooms, and following re-location of patients within the ICU. We also observed three horizontal gene transfer events between CRAB strains in the ICU, involving three different plasmids. The epidemiology of CRAB in this setting contrasted with previously described clonal outbreaks in high-income countries, highlighting the importance of environmental CRAB reservoirs in ICU epidemiology and the unique challenges in containing the spread of CRAB in ICUs where this important multidrug-resistant pathogen is endemic. This work was undertaken as part of the DETECTIVE research project funded by the Medical Research Council (MR/S013660/1), National Natural Science Foundation of China (81861138054, 32011530116, 31970128, 31770142), Zhejiang Province Medical Platform Backbone Talent Plan (2020RC075), and the National Key Research and Development Program of China grant (2018YFE0102100). W.v.S was also supported by a Wolfson Research Merit Award (WM160092).

Clonal spread of ArmA- and OXA-23-coproducing Acinetobacter baumannii International Clone 2 in Brazil during the first wave of the COVID-19 pandemic.

Introduction. Carbapenem-resistant Acinetobacter baumannii (CRAB) is the primary pathogen causing hospital-acquired infections. The spread of CRAB is mainly driven by the dissemination of resistant clones, and in Latin America, International Clones IC-1 (also known as clonal complex CC1), IC-4 (CC15) and IC-5 (CC79) are the most prevalent.Gap Statement. There are no documented outbreaks of CRAB International Clone 2 (IC-2) reported in Brazil.Aim. To describe a large outbreak of CRAB caused by the uncommon IC-2 in a Brazilian COVID-19 hospital.Methodology. From May 2020 to May 2021, 224 patients infected or colonized with CRAB were identified in a single hospital; 92 % of them were also infected with SARS-CoV-2. From these patients, 137 isolates were recovered and subjected to antimicrobial susceptibility testing, PCR analysis and molecular typing. Whole-genome sequencing and downstream analysis were carried out on a representative isolate (the first available isolate).Results. In 76 % of the patients, a single OXA-23-producing CRAB IC-2 was identified. All the isolates were susceptible to polymyxin B, but highly resistant (>95 %) to aminoglycosides, fluoroquinolones and beta-lactams. Genomic analysis revealed that the representative isolate also carried the 16S rRNA Methylase ArmA, which was detected for the first time in this species in Brazil.Conclusion. We report the rapid spread of an emerging CRAB clone responsible for causing a large outbreak in a hospital in Brazil, a country with predominance of other CRAB clones. Continuous and prospective surveillance is warranted to evaluate the impact of this clone in Brazilian hospital settings.

Molecular Epidemiology of Carbapenem-resistant Acinetobacter baumannii Isolates in a Senegalese University Teaching Hospital

Background: The emergence and spread of carbapenem-resistant Acinetobacter baumannii are critical in hospitals, particularly in intensive care units (ICUs), which represents a public health concern worldwide. In this study, we investigated the molecular epidemiology of multi-drug resistant A. baumannii (MDR-AB) in Dakar, Senegal.
 Methods. The A. baumannii was isolated from Eosin Methylene Blue Agar culture and identified using API 20NE strip test and MALDI-TOF. The antimicrobial susceptibility testing was performed using the disk diffusion method. Simplex and multiplex-polymerase chain reactions with appropriate primers were used to detect and sequence the following β-lactamase genes: Two class D carbapenem hydrolyzing oxacillinases (blaOXA-51 and blaOXA-23), three class B metallo-β-lactamase genes (blaIMP, blaVIM and blaNDM), and five class A β-lactamase genes (blaPER, blaSHV, blaVEB, blaTEM, and blaGES).
 Results: A total of 29 strains of MDR-AB were isolated from patients hospitalized at Aristide Le Dantec University teaching hospital in Dakar, Senegal. Among the 29 MDR-AB strains isolated, 11 (37.9%) were isolated from ICUs, 5 (17.2%) from pediatric surgery, and 13 (44.8%) from other departments. The MDR strains were isolated from urine and pus samples with 12 (41.4%) and 9 (31.0%), respectively. All isolates were positive for the A. baumannii specific gene blaOXA-51. The blaOXA-51 and blaOXA-23 genes coexisted in 26 (89.65%) of the strains. The blaIMP and blaVIM genes were not detected among the selected strains. Moreover1 (3.4%) strain elicited the gene coding for metallo-β-lactamase NDM-1. 2 (6.9%) isolates turned out to produce the penicillinase TEM-2.
 Conclusions: Carbapenem resistance in Senegalese strains of A. baumannii is predominantly due to the worldwide disseminated gene blaOXA-23, with a subset of strains due to NDM-1 and TEM-2. Systemic molecular surveillance network should be established for further efficient monitoring of MDR strains in Senegal.

Whole-genome analysis of carbapenem-resistant Acinetobacter baumannii from clinical isolates in Southern Thailand

The worldwide spread of carbapenem-resistant Acinetobacter baumannii (CRAB) has become a healthcare challenge for some decades. To understand its molecular epidemiology in Southern Thailand, we conducted whole-genome sequencing (WGS) of 221 CRAB clinical isolates. A comprehensive bioinformatics analysis was performed using several tools to assemble, annotate, and identify sequence types (STs), antimicrobial resistance (AMR) genes, mobile genetic elements (MGEs), and virulence genes. ST2 was the most prevalent ST in the CRAB isolates. For the detection of AMR genes, almost all CRAB isolates carried the blaOXA-23 gene, while certain isolates harbored the blaNDM-1 or blaIMP-14 genes. Also, various AMR genes were observed in these CRAB isolates, particularly aminoglycoside resistance genes (e.g., armA, aph(6)-Id, and aph(3″)-Ib), fosfomycin resistance gene (abaF), and tetracycline resistance genes (tet(B) and tet(39)). For plasmid replicon typing, RepAci1 and RepAci7 were the predominant replicons found in the CRAB isolates. Many genes encoding for virulence factors such as the ompA, adeF, pgaA, lpxA, and bfmR genes were also identified in all CRAB isolates. In conclusion, most CRAB isolates contained a mixture of AMR genes, MGEs, and virulence genes. This study provides significant information about the genetic determinants of CRAB clinical isolates that could assist the development of strategies for improved control and treatment of these infections.

Increased Capsule Thickness and Hypermotility Are Traits of Carbapenem-Resistant Acinetobacter baumannii ST3 Strains Causing Fulminant Infection.

BackgroundAcinetobacter baumannii is a successful nosocomial pathogen, causing severe, life-threatening infections in hospitalized patients, including pneumonia and bloodstream infections. The spread of carbapenem-resistant Acinetobacter baumannii (CRAB) strains is a major health threat worldwide. The successful spread of CRAB is mostly due to its highly plastic genome. Although some virulence factors associated with CRAB have been uncovered, many mechanisms contributing to its success are not fully understood.MethodsHere we describe strains of CRAB that were isolated from fulminant cases in 2 hospitals in Israel. These isolates show a rare hypermucoid (HM) phenotype and were investigated using phenotypic assays, comparative genomics, and an in vivo Galleria mellonella model. ResultsThe 3 isolates belonged to the ST3 international clonal type and were closely related to each other, as shown by Fourier-transform infrared spectroscopy and phylogenetic analyses. These isolates possessed thickened capsules and a dense filamentous extracellular polysaccharides matrix as shown by transmission electron microscopy (TEM), and overexpressed the capsule polysaccharide synthesis pathway-related wzc gene. ConclusionsThe HM isolates possessed a unique combination of virulence genes involved in iron metabolism, protein secretion, adherence, and membrane glycosylation. HM strains were more virulent than control strains in 2 G. mellonella infection models. In conclusion, our findings demonstrated several virulence factors, all present in 3 CRAB isolates with rare hypermucoid phenotypes.

Infection Control in the Era of Antimicrobial Resistance in China: Progress, Challenges, and Opportunities.

More than 3 decades have passed since infection control was implemented nationwide in China in 1986. A comprehensive set of regulations and guidelines has been developed, and almost all hospitals have established infection control teams. However, compliance is variable and is usually suboptimal. The incidence of certain multidrug-resistant organisms (MDROs), including carbapenem-resistant Acinetobacter baumannii (CRAB) and carbapenem-resistant Klebsiella pneumoniae (CRKP), is increasing, and associated infections are mainly hospital-acquired in China. Carbapenem-resistant Pseudomonas aeruginosa has remained relatively stable, whereas methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterobacter faecium have been decreasing. The spread of CRAB and CRKP in China is largely mediated by dominant high-risk lineages, namely, clonal complex 92 for CRAB and sequence type 11 for CRKP. However, challenges owing to MDROs bring opportunities for rethinking, taking coordinated action, building capacity, changing behavior, and performing studies that reflect everyday situations in the Chinese healthcare system.

The first nationwide multicenter study of Acinetobacter baumannii recovered in Serbia: emergence of OXA-72, OXA-23 and NDM-1-producing isolates

BackgroundThe worldwide emergence and clonal spread of carbapenem-resistant Acinetobacter baumannii (CRAB) is of great concern. The aim of this nationwide study was to investigate the prevalence of CRAB isolates in Serbia and to characterize underlying resistance mechanisms and their genetic relatedness.MethodsNon-redundant clinical samples obtained from hospitalized patients throughout Serbia were included in the prospective, observational, multicenter study conducted from January to June 2018. Samples were initially screened for the presence of Acinetobacter baumannii-calcoaceticus (Acb) complex using conventional bacteriological techniques. Acb complexes recovered from clinical samples obtained from inpatients with confirmed bacterial infections were further evaluated for the presence of A. baumannii. Identification to the species level was done by the detection of the blaOXA-51 gene and rpoB gene sequence analysis. Susceptibility testing was done by disk diffusion and broth microdilution method. CRAB isolates were tested for the presence of acquired carbapenemases (blaOXA-24-like, blaOXA-23-like,blaOXA-58-like, blaOXA-143-like, blaIMP, blaVIM, blaGIM, blaSPM, blaSIM, blaNDM) by PCR. Clonal relatedness was assessed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST).ResultsAcb complex was isolated in 280 out of 2401 clinical samples (11.6%). Overall, A. baumannii was identified in 237 out of 280 Acb complex (84.6%). CRAB prevalence was found to be 93.7% (237/222). The MIC50/MIC90 for imipenem and meropenem were 8/> 32 μg/mL and 16/> 32 μg/mL, respectively. Although susceptibility was high for colistin (95.7%; n = 227) and tigecycline (75.1%; n = 178), ten isolates (4.3%) were classified as pandrug-resistant. The following carbapenemases-encoding genes were found: 98 (44.2%) blaOXA-24-like, 76 (34.5%) blaOXA-23-like, and 7 (3.2%) blaNDM-1. PFGE analysis revealed six different clusters. MLST analysis identified three STs: ST2 (n = 13), ST492 (n = 14), and ST636 (n = 10). Obtained results evaluated that circulating CRAB clones in Serbia were as follows: blaOXA66/blaOXA23/ST2 (32.4%), blaOXA66/blaOXA23/blaOXA72/ST2 (2.7%), blaOXA66/blaOXA72/ST492 (37.8%), and blaOXA66/blaOXA72/ST636 (27.1%).ConclusionThis study revealed extremely high proportions of carbapenem resistance among A. baumannii clinical isolates due to the emergence of blaOXA-72, blaOXA-23, and blaNDM-1 genes among CRAB isolates in Serbia and their clonal propagation.

Molecular mechanisms of antibiotic co-resistance among carbapenem resistant Acinetobacter baumannii

The spread of carbapenem-resistant Acinetobacter baumannii (CRAB) is difficult to control especially in the hospitals due to the successful mobilization and evolution of the genetic elements harboring the resistant determinants. The study was conducted to examine the distribution of aminoglycosides, tetracycline, and sulfonamide-resistant determinants among CRAB isolates that carry the blaOXA-23 gene. For a total of 160 CRAB strains isolated at tertiary care hospitals of Pakistan that mainly carried blaOXA-23 gene were included in the study to evaluate the assortment of antibiotic resistance genes. The susceptibility rates of CRAB for other than beta-lactam drugs were 2.5% for both ciprofloxacin and aminoglycosides and 18% and 25% for sulfonamides and tetracyclines, respectively. Polymyxin B (MIC90, 1 g/mL) Colistin (MIC90, 1 g/mL) and Tigecycline (MIC90, 2 g/mL) were most active against these extensively drug-resistant CRAB isolates. The isolates were found to possess various genes mainly the tetB and sul2 for tetracycline and sulfonamide but the genes conferring resistance to aminoglycosides were varied with various combinations. Despite the CRAB clones containing blaOXA-23 have been previously reported in Pakistani hospitals, the screening of genetic determinants responsible for other antimicrobial agents is crucial for developing an effective surveillance and mitigation system for infection management.

Generation and selection of antibodies for a novel immunochromatographic lateral flow test to rapidly identify OXA-23-like-mediated carbapenem resistance in Acinetobacter baumannii.

The spread of carbapenem-resistant Acinetobacter baumannii has led to a worldwide healthcare problem. Carbapenem resistance in A. baumannii is mainly mediated by the acquisition of the carbapenem-hydrolyzing oxacillinase OXA-23. The phenotypic detection of carbapenem-producing A. baumannii is challenging and time-consuming. Hence, there is an unmet medical need for reliable and rapid diagnostic tools to detect OXA-23-producing Acinetobacter isolates to enable successful patient management. Development of an immunochromatographic lateral flow test (ICT) for the rapid and reliable detection of OXA-23-producing carbapenem-resistant Acinetobacter isolates. For the development of an antibody-based ICT, we generated anti-OXA-23 monoclonal antibodies (MoAbs) and screened them sequentially for their ability to bind native OXA-23. Selected OXA-23-specific MoAbs were tested in different combinations for their capacity to capture and detect OXA-23His6 by sandwich enzyme-linked immunosorbent assay (ELISA) and ICT. A well-characterized collection of carbapenem-resistant Acinetobacter isolates with defined carbapenem resistance mechanisms were used to evaluate the specificity of the final OXA-23 ICT prototype. The antibody pairs best suited for the sandwich ELISA format did not match the best pairs in the ICT format selected during the development process of the final prototype OXA-23 ICT. This prototype was able to differentiate between OXA-23 subfamily-mediated carbapenem resistance and carbapenem-resistant Acinetobacter isolates overexpressing other OXAs with 100 % specificity and a turnaround time of 20 min from culture plate to result. With this rapid detection assay one can save 12-48 h of diagnostic time, which could help avoid inappropriate use of carbapenems and enable earlier intervention to control the transmission of OXA-23-producing carbapenem-resistant Acinetobacter isolates to other patients and healthcare workers.

A high mortality rate associated with multidrug-resistant Acinetobacter baumannii ST79 and ST25 carrying OXA-23 in a Brazilian intensive care unit.

The global spread of carbapenem-resistant Acinetobacter baumannii (A. baumannii) strains has restricted the therapeutic options available to treat infections due to this pathogen. Understanding the prevalence of such infections and the underlying genetic mechanisms of resistance may help in the implementation of adequate measures to control and prevent acquisition of nosocomial infections, especially in an intensive care unit setting. This study describes the molecular characteristics and risk factors associated with OXA-23-producing A. baumannii infections. A case-control study was undertaken from September/2013 to April/2015. Acquisition of OXA-23-producing A. baumannii was found to be associated with the use of nasogastric tubes, haemodialysis, and the use of cephalosporins. These isolates were only susceptible to amikacin, gentamicin, tigecycline, and colistin, and contained the ISAba1 insertion sequence upstream ofblaOXA-23 and blaOXA-51 genes. Twenty-six OXA-23-producing A. baumannii strains belonged to the ST79 (CC79) clonal group,and patients infected or colonised by these isolates had a higher mortality rate (34.6%). In conclusion, this study showed a dissemination of OXA-23-producing A. baumannii strains that was associated with several healthcare-related risk factors and high mortality rates among intensive care unit patients.

Direct detection of carbapenemase-associated proteins of Acinetobacter baumannii using nanodiamonds coupled with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

The appearance and spread of carbapenem-resistant Acinetobacter baumannii (CRAB) pose a challenge for optimization of antibiotic therapies and outbreak preventions. The carbapenemase production can be detected through culture-based methods (e.g. Modified Hodge Test-MHT) and DNA based methods (e.g. Polymerase Chain Reaction-PCR). The culture-based methods are time-consuming, whereas those of PCR assays need only a few hours but due to its specificity, can only detect known genetic targets encoding carbapenem-resistance genes. Therefore, new approaches to detect carbapenemase-producing A. baumannii are of great importance. Here, we have developed a rapid and novel method using detonation nanodiamonds (DNDs) as a platform for concentration and extraction of A. baumannii carbapenemase-associated proteins prior to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF-MS) analysis. To concentrate and extract the A. baumannii carbapenemase-associated proteins, we tested several protein precipitation conditions and found a 0.5% trifluoroacetic acid (TFA) solution within the bacterial suspension could result in strong ion signals with DNDs. A total of 66 A. baumannii clinical-isolates including 51 carbapenem-resistant strains and 15 carbapenem-susceptible strains were tested. Our result showed that among the 51 carbapenem-resistant strains 49 strains had a signal at m/z ~40,279 (±87); among the 15 carbapenem-susceptible strains, 4 strains showed a signal at m/z ~40,279. With on-diamond digestion, we confirmed that the captured protein at m/z ~40,279 was related to ADC family extended-spectrum class C beta-lactamase, from A. baumannii. Using this ADC family protein as a biomarker (m/z ~ 40,279) for carbapenem susceptibility testing of A. baumannii, the sensitivity and the specificity could reach 96% and 73% as compared to traditional imipenem susceptibility testing (MIC results). However, the sensitivity and specificity of this method reached 100% as compared to polymerase chain reaction (PCR) result. Our approach could directly detect the carbapenemase-associated proteins of A. baumannii within 90 min and does not require addition of carbapenemase substrate which is required in the MHT or other mass spectrometric methods. For future applications, our method could be efficiently used in the detection of other carbapenemase-producing bacteria.

Clonal spread of carbapenem-resistant Acinetobacter baumannii across a community hospital and its affiliated long-term care facilities: A cross sectional study.

The global spread of carbapenem-resistant Acinetobacter baumannii (CRAB) is now a public health problem. In Taiwan, the relationship of the CRAB circulation between long-term care facilities (LTCFs) and acute care hospitals remains unclear. Here, we use molecular epidemiologic methods to describe the transmission of CRAB isolates between a community hospital and its affiliated LTCFs. Subjects localized in eight LTCFs who were not admitted acute care hospitals in recent a year were enrolled in this study. CRAB isolates were collected during June 1, 2015 and December 31, 2015. DNA fingerprinting was performed by repetitive extragenic palindromic sequence-based polymerase chain reaction (Rep-PCR) and multilocus sequence typing (MLST). Multiplex-PCR amplification for the detection of blaOXA genes and beta-lactamase genes was performed. Twenty one subjects were enrolled. The major hospital admission diagnoses among the 21 subjects were pneumonia (71.4%). Genotyping of CRAB isolates by Rep-PCR revealed that a major clone, designated as type III, comprised fifteen of 21 (71.4%) isolates taken from 5 LTCFs and one study hospital. The isolates with type III were subtyped by PubMLST into 4 ST types. The most prevalent blaOXA genes in these isolates were blaOXA-23-like (85.70%, 18/21). Twenty isolates carried blaSHV. CONCLUSION: Clonal spread of blaOxA-23-carrying CRABs was found around LTCFs and the affiliated hospital. In Taiwan, it is important for the government to focus attention on the importance of identifying and tracing CRAB infections in LTCFs.

Evaluation of a modified cleaning procedure in the prevention of carbapenem-resistant Acinetobacter baumannii clonal spread in a burn intensive care unit using a high-sensitivity luminometer

Enhanced environmental cleaning practices are among the most accepted measures for controlling the spread of carbapenem-resistant Acinetobacter baumannii (CR-Ab). To evaluate the impact of heightened cleaning on an ongoing CR-Ab outbreak in a burn intensive care unit (BICU) of an Italian teaching hospital, where chlorhexidine-60% isopropyl alcohol was applied as a complementary disinfectant on high-touch surfaces. Compliance with the microbial limit proposed for the BICU by AFNOR-NF-S90-351 (20 colony-forming units/100cm2) was assessed by plate count, and compared with the results obtained with intracellular adenosine triphosphate (ATP) detection. Genotyping was performed using pulsed-field gel electrophoresis. During the standard cleaning regimen, three out of 23 samples (13%) gave results over the AFNOR limit and five (21.7%) showed unacceptable ATP levels with 100 relative light units/100cm2 as the benchmark limit (sensibility 86.4%, specificity 92.2%). Following improvement of the cleaning procedure, only two samples out of 50 (4%) did not satisfy the microbiological criteria and seven (14%) exceeded the ATP limit. In a successive phase, eight of 30 samples collected showed unacceptable results (27%). Adding chlorhexidine-60% isopropyl alcohol as complementary disinfectant proved to be effective for reducing environmental microbial contamination, ATP levels and CR-Ab infection/colonization in patients admitted to the BICU. Real-time monitoring by ATP assay was useful for managing the cleaning schedule and reducing hospital infections, although the calculated values must be interpreted as cleanliness indicators rather than risk indicators.

Effect of daily chlorhexidine bathing on acquisition of carbapenem-resistant Acinetobacter baumannii (CRAB) in the medical intensive care unit with CRAB endemicity

There is insufficient evidence for daily chlorhexidine bathing to reduce nosocomial spread of carbapenem-resistant Acinetobacter baumannii (CRAB) in endemic situations. An interrupted time series study was performed to evaluate the effect of daily chlorhexidine bathing on the acquisition of CRAB in a medical intensive care unit (ICU) with CRAB endemicity. There was a 14-month control period and 12-month chlorhexidine bathing period. Segmented Poisson regression analysis was performed to assess the impact of chlorhexidine bathing on the level and trend of the series of prevalence rates and incidence density. Also, chlorhexidine susceptibility testing was performed on CRAB isolates collected during the chlorhexidine bathing period. There was a 51.8% reduction of CRAB acquisition rates after an introduction of daily chlorhexidine bathing (44.0 vs 21.2 cases/1,000 at-risk patient days, P<.001). There was a significant reduction in the level (-0.604; 95% CI,-0.904to-0.305; P<.001) of incidence density of CRAB, whereas there was no significant change in both level and trend of CRAB prevalence rates. Minimum inhibitory concentration of chlorhexidine against a total of 98 CRAB isolates ranged from 8-64 μg/mL. Daily chlorhexidine bathing significantly reduces the acquisition of CRAB in a medical ICU with CRAB endemicity.

Rapid and sensitive detection of carbapenemase activity in Acinetobacter baumannii using superficially porous liquid chromatography-tandem mass spectrometry.

The emergence and spread of carbapenem-resistant Acinetobacter baumannii poses a challenge for optimizing antibiotic therapies and preventing outbreaks. Traditional phenotypic assays such as the modified Hodge test (MHT) or polymerase chain reaction (PCR)-based detection of the carbapenemase genes are time-consuming and complicated. Therefore, new approaches for the efficient detection of carbapenemase-producing A. baumannii are urgently required. In this study, we used the superficially porous liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay to measure carbapenem hydrolysis in a solution spiked with test strains of A. baumannii. The rate of carbapenem hydrolysis during incubation was expressed as the ratio of the carbapenem peak area of the test A. baumannii strains to the noncarbapenemase-producing A. baumannii ATCC 17978. This method can accurately measure the carbapenem hydrolysis rate and, therefore, can effectively identify carbapenemase-producing strains within 75 minutes. A total of 112 A. baumannii strains were used in this study, including 103 clinical isolates with 68 carbapenem-resistant strains and 35 carbapenem-susceptible strains, seven ATCC strains and two selected mutants. The results of the superficially porous LC-MS/MS assay showed higher detection sensitivity compared to the results of the MHT. Our results demonstrate the ability of the former method to routinely detect carbapenemase-producing A. baumannii.

Emergence and spread of carbapenem-resistant Acinetobacter baumannii sequence type 191 in a Korean hospital

Emergence and spread of specific carbapenem-resistant Acinetobacter baumannii (CRAB) clones cause a serious therapeutic problem. This study was aimed to investigate the clonal diversity and genetic basis of antimicrobial resistance among the 69 CRAB isolates from 2009 to 2010 in a Korean hospital. All CRAB isolates were found to be sequence type (ST) 2 using the Institute Pasteur’s multilocus sequence typing (MLST) scheme, but classified into two sequence groups and nine pulsotypes. Fifty-six CRAB isolates belonging to two main pulsotypes were found to be ST191 using the Bartual’s MLST scheme. All CRAB isolates showed an extensively drug-resistant phenotype. The blaOXA-51/blaOXA-23, blaAmpC/blaPER-1 and armA genes were largely responsible for resistance to carbapenems, extended-spectrum β-lactams and aminoglycosides, respectively. The first CRAB strains identified in 2005 in this hospital were found to be ST2 using the Institute Pasteur’s MLST scheme, but showed ST353 using the Bartual’s MLST scheme and different pulsotypes from the CRAB isolates from 2009 to 2010. In conclusion, this is the first report of emergence and spread of A. baumannii ST191 in Korea, as well of the genetic basis of its antimicrobial resistance.

Spread of carbapenem-resistant Acinetobacter baumannii carrying a plasmid with two genes encoding OXA-72 carbapenemase in Lithuanian hospitals

To study the molecular epidemiology of Acinetobacter baumannii isolates from Lithuanian hospitals with an emphasis on the characterization of plasmids and antibiotic-resistance genes and their relationship with European clones (ECs) I and II. PFGE, PCR analysis of ECs and resistance genes, plasmid replicon typing, DNA transformation and sequencing were employed to characterize A. baumannii. Of the 444 isolates studied, 230 (52%) and 202 (45%) belonged to ECI and ECII clones, respectively, and showed clone-specific resistance gene profiles. Five plasmids from 6 to 100 kb in size in different combinations (one to four plasmids) were found in A. baumannii isolates, the combination of 9 + 70 kb plasmids in ECI isolates (60%, 137/230) and an 11 kb plasmid in ECII isolates (52%, 106/202) being the most frequent. GR2 and GR6 replicon groups, alone or in combination, were found, with a prevalence of GR2 + GR6 in ECI isolates of 90% (206/230) and a prevalence of GR2 in ECII isolates of 56% (113/202). The vast majority (95%, 165/174) of carbapenem-resistant A. baumannii ECII isolates carried a novel GR2-type plasmid of 11 kb, designated pAB120, which had two copies of a blaOXA-72 gene, flanked by XerC/XerD-like sites and conferred resistance to carbapenems when introduced into a carbapenem-susceptible A. baumannii strain. The spread of carbapenem-resistant A. baumannii in Lithuanian hospitals is strongly associated with strains belonging to ECII and carrying a GR2 plasmid encoding two blaOXA-72 genes. The genetic environment of pAB120 supports the role of site-specific recombination associated with the acquisition of carbapenem-hydrolysing class D β-lactamases.

Molecular and Epidemiological Characterization of Carbapenem-ResistantAcinetobacter baumanniiin Non-Tertiary Korean Hospitals

PurposeThe increasing prevalence and global spread of carbapenem-resistant Acinetobacter baumannii (A. baumannii) has become a serious problem. The aim of this study was to investigate molecular and epidemiological characteristics of carbapenem-resistant A. baumannii isolates collected from Korean non-tertiary hospitals.Materials and MethodsThirty six non-duplicated carbapenem-resistant A. baumannii isolates were collected from 17 non-tertiary hospitals in Korea between 2004 and 2006. Isolates were typed by multilocus sequence typing and repetitive-sequence-based PCR (rep-PCR). Detection of genes encoding OXA carbapenemase and their relationship with ISAba1 was performed by PCR.ResultsTwo clones were prevalent among 36 isolates: ST69 (17 isolates, 47.2%) and ST92 (19 isolates, 52.8%). Rep-PCR patterns were diverse and revealed that all isolates were clustered into eight band patterns. The ISAba1-activated blaOXA-23-like and ISAba1-activated blaOXA-51-like genes were prevalent among the carbapenem-resistant A. baumannii isolates.ConclusionThe class D β-lactamase genes of A. baumannii were distributed nationwide in non-tertiary Korean hospitals.

Nosocomial spread of carbapenem-resistant Acinetobacter baumannii (types ST75 and ST137) carrying blaOXA-23-like gene with an upstream ISAba1 in a Chinese hospital

The most widespread type of carbapenemases among carbapenem-resistant Acinetobacter baumannii (CRAB) belongs to the oxacillinase (OXA) group. A total of 57 CRAB isolates and 20 non-CRAB isolates (i.e., A. baumannii susceptible to carbapenems) were studied to investigate the molecular epidemiology of CRAB isolates and to identify the OXAs responsible for resistance to imipenem. The ISAba1-blaOXA-23-like gene was detected in all 57 CRAB isolates but was detected in none of the non-CRAB isolates. Pulsed-field gel electrophoresis (PFGE) revealed that clones A and B were the dominant genotypes, and all blaOXA-23-like gene positive strains were classified as either clone A or B strains. ST75 and ST137 were the most prominent sequence types (STs). Finally, the A. baumannii isolates of clone A, C and F were all demonstrated to be genetically similar to the previously identified European clone II. In conclusion, ST75- and ST137-type CRAB isolates that produced the blaOXA-23-like gene with an upstream ISAba1 contributed to the nosocomial outbreaks studied in this work.