High prevalence of the PER-1 gene among carbapenem-resistant <Emphasis Type="Italic">Acinetobacter baumannii</Emphasis> in Riyadh,Saudi Arabia

The prevalence of carbapenem-resistant Acinetobacter baumannii in Saudi Arabia and their resistance genetic mechanisms are yet to be identified. We studied the prevalence and genetic diversity of extended-spectrum beta-lactamase genes, particularly the PER-1 gene, among carbapenem-resistant A. baumannii strains from patients at a tertiary care hospital in Riyadh, Saudi Arabia between 2006 and 2014. Fresh subcultured samples were tested for antimicrobial susceptibility minimum inhibitory concentration (MIC). Total genomic DNA was extracted from each isolate and further used for polymerase chain reaction (PCR) genotyping, sequence-based typing (SBT) of PER-1 and OXA-51-like gene, and multilocus sequence typing (MLST) of positive isolates. Randomly selected clinical isolates (n = 100) were subjected to MLST. A total of 503 isolates were characterized as multidrug-resistant (MDR) using the MIC. Isolates were further PCR tested for bla _-TEM and bla _-PER-1 resistance genes (n = 503). The genotyping results showed that 68/503 (14 %) isolates were positive to bla TEM. The genotyping results of PER-1-like genes showed that 384/503 (76.3 %) were positive among MDR Acinetobacter isolates. Based on SBT, the majority of these isolates were clustered into three main groups including isolates harboring PER-1: AB11 (bla _-PER-1), isolate AB16 (bla _-PER-1), and, finally, the plasmid pAB154 (bla _-PER-7). Remarkably, many isolates were concealing the PER-1 gene and harboring the TEM resistance genes as well. MLST results for selected isolates (n = 100) identified four main sequence types (STs: 2, 19, 20, and 25) and four novel isolates (ST 486–489). We report 76.3 % prevalence of the PER-1 resistance gene among Acinetobacter clinical isolates from Riyadh, Saudi Arabia. Further work is needed to explore the clinical risks and patient outcome with such resistance related to healthcare-associated infections and investigate the genetic and molecular mechanisms that confer the MDR phenotype.     

Single-Locus-Sequence-Based Typing of blaOXA-51-like Genes for Rapid Assignment of Acinetobacter baumannii Clinical Isolates to International Clonal Lineages

Single-locus bla_OXA-51-like sequence-based typing (SBT) was evaluated for its ability to determine correctly sequence types (STs) in Acinetobacter baumannii clinical isolates, in comparison with the Pasteur''s multilocus sequence typing (MLST) reference method and 3-locus sequence typing (3-LST). The comparative study was performed in 585 multidrug-resistant (MDR) A. baumannii clinical isolates recovered from 21 hospitals located throughout Greece, Italy, Lebanon, and Turkey. The isolates belonged to nine clonal complexes (CCs) that correspond to 12 distinct sequence types (STs) and to one singleton ST. These clonal lineages predominate worldwide among nosocomial MDR A. baumannii strains. The most common clone was CC2 (ST2 and ST45; n = 278 isolates) followed by CC1 (ST1 and ST20; n = 155), CC25 (n = 65), ST78 (n = 62), CC15 (ST15 and ST84; n = 9), CC10 (n = 4), CC3 (n = 4), CC6 (n = 3), CC54 (n = 3), and CC83 (n = 2). Using the bla_OXA-51-like SBT method, all 585 isolates of the study were typed and assigned correctly to the nine CCs and the singleton ST78. The 3-LST method was not able to classify isolates belonging to CC6, CC10, CC54, and CC83, which are not yet characterized in its database. The low-cost and convenient bla_OXA-51-like SBT method, compared with 3-LST and MLST, discriminated all epidemic and sporadic lineages of our collection and could be effectively applied to type rapidly A. baumannii strains.     

Diversity in Acinetobacter baumannii isolates from paediatric cancer patients in Egypt

Acinetobacter baumannii is an important nosocomial pathogen, commonly causing infections in immunocompromised patients. It is increasingly reported as a multidrug-resistant organism, which is alarming because of its capability to resist all available classes of antibiotics including carbapenems. The aim of this study was to examine the genetic and epidemiological diversity of A. baumannii isolates from paediatric cancer patients in Egypt, by sequencing the intrinsic blaOXA–51-like gene, genotyping by pulsed-field gel electrophoresis and multi-locus sequence typing in addition to identifying the carbapenem-resistance mechanism. Results showed a large diversity within the isolates, with eight different blaOXA-51-like genes, seven novel sequence types and only 28% similarity by pulsed-field gel electrophoresis. All three acquired class-D carbapenemases (OXA-23, OXA-40 and OXA-58) were also identified among these strains correlating with resistance to carbapenems. In addition, we report the first identification of ISAba2 upstream of blaOXA-51-like contributing to high-level carbapenem resistance. This indicates the presence of several clones of A. baumannii in the hospitals and illustrates the large genetic and epidemiological diversity found in Egyptian strains.     

The Changes in Epidemiology of Imipenem-Resistant Acinetobacter baumannii Bacteremia in a Pediatric Intensive Care Unit for 17 Years

BackgroundAcinetobacter baumannii infections cause high morbidity and mortality in intensive care unit (ICU) patients. However, there are limited data on the changes of long-term epidemiology of imipenem resistance in A. baumannii bacteremia among pediatric ICU (PICU) patients.MethodsA retrospective review was performed on patients with A. baumannii bacteremia in PICU of a tertiary teaching hospital from 2000 to 2016. Antimicrobial susceptibility tests, multilocus sequence typing (MLST), and polymerase chain reaction for antimicrobial resistance genes were performed for available isolates.ResultsA. baumannii bacteremia occurred in 27 patients; imipenem-sensitive A. baumannii (ISAB, n = 10, 37%) and imipenem-resistant A. baumannii (IRAB, n = 17, 63%). There was a clear shift in the antibiogram of A. baumannii during the study period. From 2000 to 2003, all isolates were ISAB (n = 6). From 2005 to 2008, both IRAB (n = 5) and ISAB (n = 4) were isolated. However, from 2009, all isolates were IRAB (n = 12). Ten isolates were available for additional test and confirmed as IRAB. MLST analysis showed that among 10 isolates, sequence type 138 was predominant (n = 7). All 10 isolates were positive for OXA-23-like and OXA-51-like carbapenemase. Of 27 bacteremia patients, 11 were male (41%), the median age at bacteremia onset was 5.2 years (range, 0–18.6 years). In 33% (9/27) of patients, A. baumannii was isolated from tracheal aspirate prior to development of bacteremia (median, 8 days; range, 5–124 days). The overall case-fatality rate was 63% (17/27) within 28 days. There was no statistical difference in the case fatality rate between ISAB and IRAB groups (50% vs. 71%; P = 0.422).ConclusionIRAB bacteremia causes serious threat in patients in PICU. Proactive infection control measures and antimicrobial stewardship are crucial for managing IRAB infection in PICU.     

Molecular and Epidemiological Characterization of Carbapenem-Resistant Acinetobacter baumannii in Non-Tertiary Korean Hospitals

Purpose

The 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 Methods

Thirty 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.

Results

Two 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.

Conclusion

The class D β-lactamase genes of A. baumannii were distributed nationwide in non-tertiary Korean hospitals.     

Spread of carbapenem-resistant international clones of <Emphasis Type="Italic">Acinetobacter baumannii</Emphasis> in Turkey and Azerbaijan: a collaborative study

Epidemic clones of Acinetobacter baumannii, described as European clones I, II, and III, are associated with hospital epidemics throughout the world. We aimed to determine the molecular characteristics and genetic diversity between European clones I, II, and III from Turkey and Azerbaijan. In this study, a total of 112 bloodstream isolates of carbapenem-resistant Acinetobacter spp. were collected from 11 hospitals across Turkey and Azerbaijan. The identification of Acinetobacter spp. using conventional and sensitivity tests was performed by standard criteria. Multiplex polymerase chain reaction (PCR) was used to detect OXA carbapenemase-encoding genes (bla _OXA-23-like, bla _OXA-24-like, bla _OXA-51-like, and bla _OXA-58-like). Pulsed-field gel electrophoresis (PFGE) typing was used to investigate genetic diversity. The bla _OXA-51-like gene was present in all 112 isolates, 75 (67 %) carried bla _OXA-23-like, 7 (6.2 %) carried bla _OXA-58-like genes, and 5 (4.5 %) carried bla _OXA-24-like genes. With a 90 % similarity cut-off value, 15 clones and eight unique isolates were identified. The largest clone was cluster D, with six subtypes. Isolates from clusters D and I were widely spread in seven different geographical regions throughout Turkey. However, F cluster was found in the northern and eastern regions of Turkey. EU clone I was grouped within J cluster with three isolates found in Antalya, Istanbul, and Erzurum. EU clone II was grouped in the U cluster with 15 isolates and found in Kayseri and Diyarbak?r. The bla _OXA-24-like gene in carbapenemases was identified rarely in Turkey and has been reported for the first time from Azerbaijan. Furthermore, this is the first multicenter study in Turkey and Azerbaijan to identify several major clusters belonging to European clones I and II of A. baumannii.     

Carbapenem resistance and acquired class D beta-lactamases in Acinetobacter baumannii from Croatia 2009–2010

The molecular epidemiology and the genetic basis of carbapenem resistance was investigated in 185 Acinetobacter baumannii isolates obtained from 13 centers of northern Croatia and Istria during 2009–2010. All isolates were multidrug-resistant, and 35 % (n?=?64) were resistant to both imipenem and meropenem. ISAba1-driven overexpression of the intrinsic bla _OXA-51-like gene was observed in all carbapenem resistant isolates, and 69 % of these (n?=?44) also produced acquired OXA-type carbapenemases. The presence of bla _OXA-58-like, bla _{OXA-24/40-like}, and bla _OXA-23-like genes was demonstrated in 33 % (n?=?21), 27 % (n?=?17) and 9 % (n?=?6) of carbapenem-resistant isolates, respectively. None of the isolates harbored the bla _IMP, bla _VIM, bla _SIM, bla _NDM or bla _PER β-lactamase genes, while bla _TEM-1 was detected in five carbapenem- and ampicillin/sulbactam-resistant isolates. Sequence group determination showed a high prevalence (81 %) of isolates belonging to the International clonal lineage (ICL)-I, although the majority (80 %) of isolates carrying acquired carbapenemase genes belonged to the ICL-II. Random amplified polymorphic DNA analysis and multilocus-sequence typing of a subset of carbapenem-resistant isolates revealed a low degree of genetic variability within both ICL-I and ICL-II populations, irrespective of the genetic basis of carbapenem resistance. Overall, an increasing trend toward carbapenem resistance was observed for A. baumannii in Croatia, and the emergence of ICL-II strains producing a variety of acquired carbapenemases.     

Characterization of Epidemiologically Unrelated Acinetobacter baumannii Isolates from Four Continents by Use of Multilocus Sequence Typing,Pulsed-Field Gel Electrophoresis,and Sequence-Based Typing of blaOXA-51-like Genes

This study used a diverse collection of epidemiologically unrelated Acinetobacter baumannii isolates to compare the robustness of a multilocus sequence typing (MLST) scheme, based on conserved regions of seven housekeeping genes, gltA, gdhB, recA, cpn60, rpoD, gyrB, and gpi, with that of sequence-based typing of bla_OXA-51-like genes (SBT-bla_OXA-51-like genes). The data obtained by analysis of MLST and SBT-bla_OXA-51-like genes were compared to the data generated by pulsed-field gel electrophoresis (PFGE). The topologies of the phylogenetic trees generated for the gyrB and gpi genes showed evidence of recombination and were inconsistent with those of the trees generated for the other five genes. MLST identified 24 sequence types (STs), of which 19 were novel, and 5 novel alleles. Clonality was demonstrated by eBURST analysis and standardized index of association values of >1 (P < 0.001). MLST data revealed that all isolates harboring the major bla_OXA-51-like alleles OXA-66, OXA-69, and OXA-71 fell within the three major European clonal lineages. However, the MLST data were not always in concordance with the PFGE data, and some isolates containing the same bla_OXA-51-like allele demonstrated <50% relatedness by PFGE. It was concluded that the gyrB and gpi genes are not good candidates for use in MLST analysis and that a SBT-bla_OXA-51-like gene scheme produced results comparable to those produced by MLST for the identification of the major epidemic lineages, with the advantage of having a significantly reduced sequencing cost and time. It is proposed that studies of A. baumannii epidemiology could involve initial screening of bla_OXA-51-like alleles to identify isolates belonging to major epidemic lineages, followed by MLST analysis to categorize isolates from common lineages, with PFGE being reserved for fine-scale typing.Acinetobacter baumannii is a Gram-negative bacterium that causes serious nosocomial infections, especially in critical care units (13, 14, 42). Several outbreaks have been caused by multidrug-resistant (MDR) strains of A. baumannii (23, 33, 43), and the rate of resistance to carbapenems, which have been the antibiotics of choice to treat infections caused by this pathogen, has increased considerably over the last decade (4, 32, 42, 46). In addition, the prevalence of A. baumannii in hospitals has increased worldwide (3, 25, 28, 29, 47), and, therefore, finding suitable molecular typing methods for A. baumannii is essential for epidemiological investigations and infection control studies. Many genomic typing methods have been used, including ribotyping (36), infrequent-restriction-site analysis (48), repetitive extragenic palindromic sequence-based PCR (rep-PCR) (18), random amplified polymorphic DNA (RAPD) analysis (21), amplified fragment length polymorphism (AFLP) analysis (39), and multilocus PCR and electrospray ionization mass spectrometry (PCR/ESI-MS) (6). Pulsed-field gel electrophoresis (PFGE) is still considered the “gold standard” for the typing of bacterial isolates (36), but it has drawbacks when its comes to interchanging data among laboratories for comparison purposes (35) and may lose its discriminatory power when isolates from geographically diverse areas are analyzed.Multilocus sequence typing (MLST) schemes, which use several housekeeping genes, have already been used to type many pathogenic bacteria (15, 17, 20, 40), including A. baumannii (1, 31, 44), and MLST is emerging as an alternative to PFGE. MLST is used mainly for global epidemiology studies, but it has also been used successfully for short-term investigation of an outbreak of meningococcal disease (11). Although MLST has many advantages over other molecular typing methods, many questions remain to be answered, including whether several loci are required to obtain a robust scheme and whether the criteria for the selection of the housekeeping genes are sufficiently reliable to reveal the population structure of the strains analyzed.bla_OXA-51-like genes are unique to A. baumannii and may be used as markers for identification of this species (16). They have also successfully been used as one of three loci in a PCR-based typing scheme that is able to assign isolates of A. baumannii to sequence groups (SGs) that appear to correlate with the major epidemic lineages within the species (41). This raises the question of whether the bla_OXA-51-like genes themselves could be utilized in a typing scheme. Accordingly, the aim of this work was to investigate the robustness of MLST in categorizing epidemiologically unrelated A. baumannii isolates from four continents and to evaluate the use of variations within the intrinsic bla_OXA-51-like gene as a typing tool comparable to MLST.     

Molecular Epidemiology of Carbapenem-Resistant Acinetobacter baumannii Isolates in the Gulf Cooperation Council States: Dominance of OXA-23-Type Producers

The molecular epidemiology and mechanisms of resistance of carbapenem-resistant Acinetobacter baumannii (CRAB) were determined in hospitals in the states of the Cooperation Council for the Arab States of the Gulf (Gulf Cooperation Council [GCC]), namely, Saudi Arabia, United Arab Emirates, Oman, Qatar, Bahrain, and Kuwait. Isolates were subjected to PCR-based detection of antibiotic resistance genes and repetitive sequence-based PCR (rep-PCR) assessments of clonality. Selected isolates were subjected to multilocus sequence typing (MLST). We investigated 117 isolates resistant to carbapenem antibiotics (either imipenem or meropenem). All isolates were positive for OXA-51. The most common carbapenemases were the OXA-23-type, found in 107 isolates, followed by OXA-40-type (OXA-24-type), found in 5 isolates; 3 isolates carried the ISAba1 element upstream of bla_OXA-51-type. No OXA-58-type, NDM-type, VIM-type, or IMP-type producers were detected. Multiple clones were detected with 16 clusters of clonally related CRAB. Some clusters involved hospitals in different states. MLST analysis of 15 representative isolates from different clusters identified seven different sequence types (ST195, ST208, ST229, ST436, ST450, ST452, and ST499), as well as three novel STs. The vast majority (84%) of the isolates in this study were associated with health care exposure. Awareness of multidrug-resistant organisms in GCC states has important implications for optimizing infection control practices; establishing antimicrobial stewardship programs within hospital, community, and agricultural settings; and emphasizing the need for establishing regional active surveillance systems. This will help to control the spread of CRAB in the Middle East and in hospitals accommodating transferred patients from this region.     

Epidemiological characterization and distribution of carbapenem-resistant Acinetobacter baumannii clinical isolates in Italy

This study was aimed at tracing the molecular characteristics of carbapenem-resistant Acinetobacter baumannii (CRAB) clinical isolates in Italy with both pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Two hundred and two CRAB isolates were collected during 2004–2009, in two different surveillance periods, from 22 Italian hospitals that were representative for both distribution and infection. PFGE was performed, and the MLST scheme used was based on the gene sequence as published on the MLST Pasteur website http://www.pasteur.fr/mlst. Representatives of the major European clones I (RUH 875) and II (RUH 134) were used as controls. The two groups of isolates were characterized for their carbapenem resistance genes: 154 of 202 carried bla_OXA-58 alone, 21 of 202 also carried bla_OXA-23, and 27 of 202 carried bla_OXA-23 alone. No isolates were positive for bla_OXA-24. Genotype analysis of all isolates identified four distinct patterns by PFGE, which correlated with four distinct sequence types (STs) by MLST. The distribution of these four clusters in Italy confirmed the propensity of A. baumannii for nosocomial cross-transmission in a vast geographical area. We observed that clones A and B had similarities with European clone II and I respectively. By MLST, clone A was ST2, like European clone II, and clone B was ST1, like European clone I. PFGE and MLST showed the same discriminatory power and reproducibility. In addition, the two methods were concordant in defining CRAB Italian clones and in correlating them with the two pan-European clones.     

Epidemic Diffusion of OXA-23-Producing Acinetobacter baumannii Isolates in Italy: Results of the First Cross-Sectional Countrywide Survey

Carbapenem-resistant Acinetobacter baumannii (CRAb) is emerging worldwide as a public health problem in various settings. The aim of this study was to investigate the prevalence of CRAb isolates in Italy and to characterize their resistance mechanisms and genetic relatedness. A countrywide cross-sectional survey was carried out at 25 centers in mid-2011. CRAb isolates were reported from all participating centers, with overall proportions of 45.7% and 22.2% among consecutive nonreplicate clinical isolates of A. baumannii from inpatients (n = 508) and outpatients (n = 63), respectively. Most of them were resistant to multiple antibiotics, whereas all remained susceptible to colistin, with MIC₅₀ and MIC₉₀ values of ≤0.5 mg/liter. The genes coding for carbapenemase production were identified by PCR and sequencing. OXA-23 enzymes (found in all centers) were by far the most common carbapenemases (81.7%), followed by OXA-58 oxacillinases (4.5%), which were found in 7 of the 25 centers. In 6 cases, CRAb isolates carried both bla_OXA-23-like and bla_OXA-58-like genes. A repetitive extragenic palindromic (REP)-PCR technique, multiplex PCRs for group identification, and multilocus sequence typing (MLST) were used to determine the genetic relationships among representative isolates (n = 55). Two different clonal lineages were identified, including a dominant clone of sequence type 2 (ST2) related to the international clone II (sequence group 1 [SG1], SG4, and SG5) and a clone of ST78 (SG6) previously described in Italy. Overall, our results demonstrate that OXA-23 enzymes have become the most prevalent carbapenemases and are now endemic in Italy. In addition, molecular typing profiles showed the presence of international and national clonal lineages in Italy.     

Outbreaks of Imipenem Resistant Acinetobacter Baumannii Producing OXA-23 ��-Lactamase in a Tertiary Care Hospital in Korea

Purpose

Since November 2006, imipenem-resistant Acinetobacter baumannii isolates have increased in Kyung Hee University Hospital in Seoul, Korea. The purpose of this study was to determine the genetic basis and molecular epidemiology of outbreak isolates.

Materials and Methods

Forty-nine non-repetitive isolates of the 734 IRAB strains were investigated in order to determine their characteristics. The modified Hodge and the ethylenediaminetetraacetic acid (EDTA)-disk synergy test were performed for the screening of carbapenemase and metallo-β-lactamase production. Multiplex polymerase chain reaction (PCR) assays were performed for the detection of genes encoding for OXA-23-like, OXA-24-like, OXA-58-like and OXA-51-like carbapenemase. Pulsed-field gel electrophoresis (PFGE) was performed for strain identification.

Results

All isolates showed 100% resistance to ciprofloxacin and gentamicin, 97.9% resistance to cefepime, piperacillin/tazobactam, aztreonam, ceftazidime and piperacillin, 93.9% resistance to tobramycin and 57.1% resistance to amikacin. All of the 49 isolates (100%) showed positive results in the modified Hodge test and negative results in the EDTA-disk synergy test. They all (100%) possessed the encoding gene for an intrinsic OXA-51-like carbapenemase and an acquired OXA-23-like carbapenemase in the multiplex PCR assay. PFGE patterns revealed that all isolates were clonally related from A1 to A14.

Conclusion

It is concluded that all of the 49 IRAB isolates acquired resistance to imipenem by producing OXA-23 carbapenemase and they might have originated from a common source.     

The emergence and dissemination of CTX-M-producing Escherichia coli sequence type 131 causing community-onset bacteremia in Israel

Community-onset bloodstream infections caused by extended-spectrum β-lactamase-producing Escherichia coli (ESBL-EC-COBSIs) were investigated over a 7-year-period (2003–2009) in our institution. ESBL-EC-COBSI inclusion criteria were cefotaxime/ceftazidime non-susceptible blood isolates recovered during 48 h upon hospital admission. Forty-one isolates were molecularly characterized. Susceptibilities were determined (Vitek-2) and genotyping was performed [multilocus sequence typing (MLST)]. CTX-M genes were determined [polymerase chain reaction (PCR) and sequencing] and bla _CTX-M-encoding plasmids (n?=?10) were analyzed and compared. Phylogrouping and virulence genes were identified (PCR). The incidence rate of ESBL-EC-COBSIs has increased from 2.94 to 7.87 cases/10,000 admissions. All isolates were multidrug-resistant (MDR), displaying co-resistance to ciprofloxacin (93 %), trimethoprim–sulfamethoxazole (85 %), and gentamicin (51 %). MLST identified ten sequence types (STs), of which five were novel. ST131 accounted for 66 % of the cases (27/41), and dominated over the years (prevalence of 25 % in 2003 and 85 % in 2009). All isolates carried CTX-M genes with the following prevalence: bla _CTX-M-2 (6/8; 75 %) in 2003; bla _CTX-M-15 (9/13, 69 % in 2007); and bla _CTX-M-15 (11/20, 55 %) and bla _CTX-M-14 (7/20, 35 %) in 2009. bla _CTX-M-15- and bla _CTX-M-14-encoding plasmids harbored by ST131 differed. Of all isolates, 98 % belonged to virulent phylogroups B2 (28/41, 68 %) and D (12/41, 29 %), though ST131 isolates carried a higher number of virulence genes compared to other lineages (p?<?0.05). The incidence of ESBL-EC-COBSIs increased 2.7-fold during the period 2003–2009. This increase appears to be related to the emergence and clonal expansion of bla _CTX-M-15- or bla _CTX-M-14-carrying ST131. The superiority of this virulent lineage should be further explored.     

OXA-51-like β-lactamases and their association with particular epidemic lineages of Acinetobacter baumannii

Sixty diverse clinical Acinetobacter baumannii isolates of worldwide origin were assigned to sequence groups, based on a multiplex PCR for the ompA , csuE and bla _OXA-51-like genes. The majority (77%) of isolates belonged to sequence groups 1 and 2 (SG1 and SG2), with sequence group 3 (SG3) and non-grouped isolates accounting for the remainder. The isolates were not closely related according to pulsed-field gel electrophoresis (PFGE), and the majority were sensitive to imipenem and meropenem. The construction of a linkage map of OXA-51-like β-lactamase sequence relationships revealed two closely related clusters of enzymes, one focused around OXA-66 and the other around OXA-69. Isolates belonging to SG1 encoded an enzyme from the OXA-66 cluster, while those belonging to SG2 encoded an enzyme from the OXA-69 cluster. All SG3 isolates encoded OXA-71, which does not form part of a close enzyme grouping. Major multinational lineages accounted for a significant proportion of A. baumannii clinical isolates, and the evolution of the OXA-51-like enzymes appears to be an ongoing process.     

Dissemination of New Delhi metallo-β-lactamase-1-producing Acinetobacter baumannii in Europe

Multidrug-resistant and New Delhi metallo-β-lactamase I (NDM-I) -producing Acinetobacter baumannii are increasingly reported. A collection of five NDM-I-positive A. baumannii isolates recovered in four European countries were analysed. Genotyping was performed by pulsed-field gel electrophoresis, multiplex PCR sequence typing, Diversilab and multilocus sequence typing. Three distinct sequence types were identified. All isolates harboured a chromosomally located bla_NDM-1. gene within a Tn/25-like transposon. One isolate co-expressed another unrelated carbapenemase OXA-23. This report constitutes the first epidemiological study of NDM-I-producing A. baumannii from four countries.     

Prevalence of carbapenem-hydrolyzing class D β-lactamase genes in Acinetobacter spp. isolates in China

In order to assess the prevalence of carbapenem-hydrolyzing class D β-lactamase genes in Acinetobacter spp. isolates in China, we conducted a polymerase chain reaction (PCR)-based surveillance of OXA-type β-lactamase gene clusters for a total of 2,880 Acinetobacter spp. isolates collected from 23 Chinese provinces. All isolates were tested for susceptibility to 12 antimicrobial agents and showed high rates of resistance to all these agents except minocycline. We also found that the vast majority of carbapenem-resistant Acinetobacter spp. were OXA-23-like-producing isolates, predominantly Acinetobacter baumannii isolates. Besides, bla _OXA-58-like and bla _OXA-24-like genes were detected in 32 and 11 isolates, respectively, involving many provinces throughout China. Furthermore, these two carbapenem-resistance determinants were located on transferable plasmids in most cases, indicating an emerging threat for both OXA-58-like- and OXA-24-like-producing Acinetobacter spp. isolates in China. Interestingly, a novel homologue of the bla _OXA-143 gene was identified in a susceptible Acinetobacter pittii isolate. Overall, these observations suggest that the bla _OXA-23-harboring A. baumannii isolates are the most frequent carbapenem-resistant Acinetobacter spp. in China, and the bla _OXA-24-like and bla _OXA-58-like genes have emerged as potential threats of hospital outbreaks of multidrug-resistant Acinetobacter spp.     

French regional surveillance program of carbapenemase-producing Gram-negative bacilli: results from a 2-year period

In February 2011, the CARB-LR group was created as a sentinel laboratory-based surveillance network to control the emergence of carbapenem-resistant Gram-negative bacilli (CR GNB) in a French Southern Region. We report the epidemiological results of a 2-year study. All the Gram-negative bacilli isolates detected in the different labs (hospital and community settings) of a French Southern Region and with reduced susceptibility to ertapenem and/or imipenem were characterised with regard to antibiotic resistance, bla genes content, repetitive sequence-based polymerase chain reaction (rep-PCR) profiles and multilocus sequence typing (MLST). A total of 221 strains were analysed. Acinetobacter baumannii was the most prevalent carbapenemase-producing bacteria, with a majority of OXA-23 producers (n?=?37). One isolate co-produced OXA-23 and OXA-58 enzymes. Klebsiella pneumoniae was the most frequent carbapenemase-producing Enterobacteriaceae (CPE) (OXA-48 producer: n?=?29, KPC producer: n?=?1), followed by Escherichia coli (OXA-48 producer: n?=?8, KPC producer: n?=?1) and Enterobacter cloacae (OXA-48 producer, n?=?1). One isolate of Pseudomonas aeruginosa produced a VIM-1 carbapenemase. A clonal diversity of carbapenemase-producing K. pneumoniae and E. coli was noted with different MLSTs. On the other hand, almost all OXA-23-producing A. baumannii strains belonged to the widespread ST2/international clone II. The link between the detection of CR GNB and a foreign country was less obvious, suggesting the beginning of a local cross-transmission. The number of CR GNB cases in our French Southern Region has sharply increased very recently due to the diffusion of OXA-48 producers.     

OXA-51-like beta-lactamases and their association with particular epidemic lineages of Acinetobacter baumannii.

Sixty diverse clinical Acinetobacter baumannii isolates of worldwide origin were assigned to sequence groups, based on a multiplex PCR for the ompA, csuE and bla(OXA-51-like) genes. The majority (77%) of isolates belonged to sequence groups 1 and 2 (SG1 and SG2), with sequence group 3 (SG3) and non-grouped isolates accounting for the remainder. The isolates were not closely related according to pulsed-field gel electrophoresis (PFGE), and the majority were sensitive to imipenem and meropenem. The construction of a linkage map of OXA-51-like beta-lactamase sequence relationships revealed two closely related clusters of enzymes, one focused around OXA-66 and the other around OXA-69. Isolates belonging to SG1 encoded an enzyme from the OXA-66 cluster, while those belonging to SG2 encoded an enzyme from the OXA-69 cluster. All SG3 isolates encoded OXA-71, which does not form part of a close enzyme grouping. Major multinational lineages accounted for a significant proportion of A. baumannii clinical isolates, and the evolution of the OXA-51-like enzymes appears to be an ongoing process.     

Clonal relationship and the association of the ST218 strain harboring blaOXA-72 gene to mortality in carbapenem-resistant Acinetobacter baumannii bacteremia

Background/purpose

In 2017, the World Health Organization categorized carbapenem-resistant Acinetobacter baumannii (CRAB) as a priority 1, critical antibiotic-resistant bacteria. This study analyzed the clinical outcomes and investigated the molecular epidemiology of CRAB bacteremia in a medical center in Northern Taiwan.

OXA beta-lactamase-mediated carbapenem resistance in Acinetobacter baumannii

Objectives: Acinetobacter baumannii is a significant pathogen in health care settings. In recent years, an increase in carbapenem resistance among A. baumannii due to Ambler class B metallo-beta-lactamases or class D OXA carbapenamases has been reported. In this study we detected the presence of OXA carbapenamases and coproduction of metallo-beta-lactamases (bla_VIMand bla_IMP) by phenotypic and genotypic methods in carbapenem resistant clinical isolates of Acinetobacter baumannii. Materials and Methods: A total of 116 consecutive, non-duplicate carbapenem resistant A. baumannii isolated from various clinical specimens were included in the study. The modified Hodge test and inhibitor potentiated disk diffusion tests were done for the screening of carbapenamase and metallo-beta-lactamase production, respectively. Polymerase chain reaction (PCR) was performed for the detection of OXA (bla_{OXA 23} like, bla_OXA-24 like, bla_OXA-51 like and bla_OXA-58 like genes) and metallo-beta-lactamases (bla_VIMand bla_IMP) genes. Gene sequencing was performed for representative isolates. Results: Among 116 A. baumannii, OXA genes were detected in 106 isolates. Bla_{OXA 51} like (n = 99) and bla_{OXA -23} like (n = 95) were the most common and they coexisted in 89 isolates. bla_OXA-24 like gene was detected in two isolates of which one also carried bla_OXA-51 like and bla_OXA-58 like genes. The modified Hodge test was positive in 113 isolates. The metallo-beta-lactamase screening test was positive in 92 isolates. bla_vimwas detected in 54 isolates of which 1 also carried the bla_IMP gene. Conclusions: bla_OXA-23 like and bla _{OXA 51} like genes are the most common types of OXA carbapenamases while the bla_VIMtype is the most common type of metallo-beta-lactamase contributing to carbapenem resistance in clinical isolates of A. baumannii. The coproduction of OXA and metallo-beta-lactamases is not an uncommon phenomenon in A. baumannii.