OXA Genes Research Articles

Investigations on the genomic diversity of OXA from isolated Acinetobacter baumannii.

We distinguished the four OXA-type carbapenemase subgroup alleles present in 120 strains of Acinetobacter baumannii by using polymerase chain reaction (PCR) and investigated the distributions of the OXA subgroups in clinically isolated samples. Amplification of the OXA genes blaOXA-23, blaOXA-24, blaOXA-51, and blaOXA-58 was performed by multiplex PCR. Antibiotics susceptibility test was conducted for determine the sensitivity of the A. baumannii to clinical common used antibiotics by Kirby-Bauer method. Results revealed that 46 (51.69%) of the samples were positive for only the blaOXA51 gene and 41 (46.07%) were positive for both the blaOXA51 and blaOXA58 genes in the 89 isolates of A. baumannii. Among these, 45 were carbapenem-resistant and 44 carbapenem-sensitive. Strains containing either blaOXA51 or blaOXA58 showed resistance or sensitivity to carbapenems, respectively. A. baumannii isolated from intensive care units showed significantly higher resistance rate to Cefepime, Piperacillin-tazobactam, Amikacin, Ceftazidime, Cefotaxime, Sulfamethoxazole-trimethoprim, and Gentamicin than those isolated from other departments (P < 0.05). In conclusion, we found that the presence of blaOXA-51 and blaOXA-58 appears to convey a mechanism of resistance or sensitivity to carbapenems, respectively, in A. baumannii clinical isolates.

Epidemiology of infections caused by carbapenemase-producing Enterobacteriaceae: Reservoirs and transmission mechanisms

The dissemination of carbapenemase-producing Enterobacteriaceae has occurred very quickly and has crossed borders rapidly between countries and continents. In some areas, it has exceeded the holding capacity of health systems, reaching epidemic proportions. This form of dissemination has not been the same for all enzymes, with KPC, NDM and OXA-48 genes having a greater ability to spread. These enzymes have primarily been spread clonally in the case of KPC-producing Klebsiella pneumoniae from the initial epicenter located in New York, with a very small number of strains causing outbreaks. For NDM and OXA- 48, these resistance determinants have been vehiculized by clones with a high transmission capacity; however, simultaneous horizontal transmission is also playing an important role. The most important identified reservoirs are colonized or infected individuals from endemic areas or centers with outbreaks, but the contaminated goods from these endemic areas also play a part. An international effort is needed to control the spread of these multiresistant pathogens.

The Epidemiology and Resistance Mechanisms of Acinetobacter baumannii Isolates from the Respiratory Department ICU of a Hospital in China

Acinetobacter baumannii is an important nosocomial pathogen able to cause severe infections in an intensive care unit (ICU). However, there is a lack of analysis regarding the epidemiology and resistance of A. baumannii in respiratory department ICUs. In this study, clinical isolates were collected from the respiratory department ICU of Southwest Hospital from January 2009 to December 2010, and the social and demographic information of the patients from whom the isolates were taken was obtained from the Southwest Hospital information system. The minimal inhibitory concentration (MIC) of the isolates was determined by the agar dilution method. The carbapenemase-encoding resistance genes of these isolates were amplified using PCR. The clonal relationship of isolates was analyzed by pulsed-field gel electrophoresis (PFGE). Forty-six isolates were collected from the respiratory department ICU, and the antibiotics minocycline and quinolone had higher drug sensitivity against these isolates. The OXA-51, OXA-23, and IMP-4 genes were present at rates of 100% (46/46), 67.4% (31/46), and 41.3% (19/46), respectively. Forty-six isolates had 12 different PFGE genotypes. The results above suggested that the hospital environment and patients contributed to nosocomial infections, and the spread of resistance genes in the hospital was common.

Characterization of resistance genes in 68 ESBL-producing Klebsiella pneumonia in Lebanon

AimWe studied 68 ESBL-producing Klebsiella pneumoniae strains isolated in Lebanon, determined their profile of resistance to antibiotics, and identified 6 ESBL genes. MethodologyThe susceptibility to antibiotics was determined by the disk diffusion method. The MIC of carbapenems and cefepime was determined by the agar dilution method. ESBL genes were detected by PCR. ResultsA percentage of 88.2% and 86.7% of isolates carried the SHV and CTX-M gene respectively; combinations of more than 1 gene of resistance were detected in several isolates. Five strains were resistant to carbapenems; 4/5 carried the OXA-48 gene. ConclusionOur study revealed the emergence of K. pneumoniae ESBL (+) strains carrying several types of genes involved in this phenotype; we also identified carbapenem-resistant strains due to the OXA-48 gene, which are a real threat for public health, especially in Lebanon.

Multi-drug carbapenem-resistant Klebsiella pneumoniae infection carrying the OXA-48 gene and showing variations in outer membrane protein 36 causing an outbreak in a tertiary care hospital in Riyadh, Saudi Arabia

To investigate the genes of antibiotic resistance among isolates from the first reported carbapenem-resistant Klebsiella pneumoniae (CRKP) outbreak in a tertiary care hospital, Riyadh, Saudi Arabia. Antimicrobial susceptibility testing was performed on bacterial isolates using the Microscan Walkaway system (Siemens, Germany) and was confirmed by Etest (AB Biodisk, Sweden). bla-CTX-M, -SHV, -TEM, -OXA-48, OXA-A,B,C,D, -KPC, -NDM, -VIM, -IMP, integron 1, and outer membrane proteins(Omp)-35 and Omp-36 were investigated by PCR amplification and direct sequencing of PCR products. Isolates were sequence-typed by multilocus sequence typing (MLST). All isolates were resistant to cefotaxime, ceftazidime, cefepime, ciprofloxacin, and piperacillin-tazobactam, and 91% (21 out of 23) were resistant to amikacin and gentamicin. All isolates except two from a single patient were resistant to one of the carbapenems. CTX-M and SHV genes were detected in all isolates, CTX-M-15 and SHV-1 types being predominant among these extended-spectrum beta-lactamases (ESBLs). TEM-1 was found in all except one isolate (isolate 3). Significantly, the OXA-48 gene was also found in all isolates. OXA-D-gene was found in three out of 23 isolates. KPC, NDM, OXA-A, -B, -C, VIM, and IMP genes were absent in all isolates. Disruption of the Omp-36 gene due to insertion of transposon IS903 and/or IS4 was detected in four out of 23 isolates, and some unique variations were also observed in this gene, including an insertion of two amino acids in the L3 region of Omp-36 in one isolate (isolate 3) and a mutation resulting in a premature stop codon in another isolate (isolate 25). MLST revealed ST29 to be the predominant sequence type (17 out of 23 isolates, 74%). Three were ST709 and one each was ST37 and ST111; one isolate had an unknown ST. This is probably the first reported outbreak of multidrug/carbapenem-resistant Klebsiella infection involving the OXA-48 gene from Saudi Arabia. Although the presence of ESBLs such as OXA, CTX-M, TEM, and SHV are predictable reasons for resistance, variations in the Omp-36 gene might also have precipitated this phenomenon. Disruption of the Omp-36 sequence by large insertional elements, the insertion of two amino acids in a very crucial part of this protein, and the presence of a premature stop codon in one isolate might have rendered this protein incomplete and non-functional. The study also demonstrated that more than one type of clone was responsible for this reported apparent outbreak and that ST29, a clone not reported from this region before, was the major clone responsible.

Presence of OXA-type enzymes in Achromobacter insuavis and A. dolens.

The accurate species identification of Achromobacter isolates is difficult and the clinical isolates of this genus are mostly referred as A. xylosoxidans. Here, we report new OXA variants in 2 isolates identified as A. insuavis (A114, A79) and 1 isolate identified as A. dolens (A336). These results suggest that different bla OXA genes are ubiquitous in the different species of Achromobacter spp. The role of the other species of Achromobacter in clinical samples needs to be reevaluated, and the proper identification is absolutely necessary to understand the epidemiology of this genus.

Molecular Analysis of OXA-48-Carrying Conjugative IncL/M-Like Plasmids in Clinical Isolates of Klebsiella pneumoniae in Ireland

This study characterized an IncL/M-like plasmid containing a bla(OXA-48)-encoding gene from a clinical isolate of Klebsiella pneumoniae, denoted as E71T. Investigation of this plasmid sequence identified unique regions of interest along with conserved regions detected in eight other clinical carbapenem-resistant isolates. A 63-kb plasmid (pE71T) from K. pneumoniae E71T was sequenced and found to be highly similar to the recently published K. pneumoniae pOXA-48a (JN626286). Two copies of the insertion sequence element IS1R were identified, one of which was located adjacent to the bla(OXA-48)-encoding gene forming part of a composite transposon Tn1999.2 and the second located 16-kb downstream. Plasmid profiling and PCR assays confirmed that the pE71T backbone was conserved among the eight other clinical bla(OXA-48)-positive isolates, and in all cases, the OXA-48 genes were part of the Tn1999.2 composite transposon. This is the first report of a bla(OXA-48) and IS1R arrangement-containing plasmid in Ireland.

Genetic diversity of OXA-51-like genes among multidrug-resistant Acinetobacter baumannii in Riyadh, Saudi Arabia

We explore the genetic diversity of class D oxacillinases, including OXA-23, -24 (-40), -58 and, particularly, the intrinsic OXA-51-like genes, among multidrug-resistant (MDR) Acinetobacter baumannii strains from inpatients at a tertiary care hospital in Riyadh, Saudi Arabia. Sequence-based typing (SBT) of the OXA-51-like gene was carried out on 253 isolates. Selected isolates (n = 66) were subjected to multilocus sequence typing (MLST). The polymerase chain reaction (PCR) typing results showed that all isolates (n = 253) contained the OXA-51-like and OXA-23 genes. However, the OXA-58 gene was detected in five isolates. Further, none of the isolates had the OXA-40 (identical to the OXA-24) gene. SBT revealed a high OXA-51-like genotypic diversity and showed that all isolates were clustered into four main groups: OXA-66 (62.3 %), followed by OXA-69 (19.1 %), OXA-132 (7.6 %) and other OXA-51-like genes (10.3 %), including OXA-79, -82, -92, -131 and -197. MLST revealed four main sequence types (STs), 2, 19, 20 and 25, among the isolates, in addition to six isolates with newly designated ST194-ST197 singletons. Further, a high prevalence (81.4 %) of OXA-66 and OXA-69-like genes in A. baumannii was identified. More studies are essential in order to explore the molecular mechanisms that confer carbapenem-resistant phenotypes for A. baumannii isolates and to investigate the genetic diversity of other OXA-D genes.

Potential Impact of a Microarray-Based Nucleic Acid Assay for Rapid Detection of Gram-Negative Bacteria and Resistance Markers in Positive Blood Cultures

We evaluated the Verigene Gram-negative blood culture (BC-GN) test, a microarray that detects Gram-negative bacteria and several resistance genes. A total of 102 positive blood cultures were tested, and the BC-GN test correctly identified 97.9% of the isolates within its panel. Resistance genes (CTX-M, KPC, VIM, and OXA genes) were detected in 29.8% of the isolates, with positive predictive values of 95.8% (95% confidence interval [CI], 87.7% to 98.9%) in Enterobacteriaceae and 100% (95% CI, 75.9% to 100%) in Pseudomonas aeruginosa and negative predictive values of 100% (95% CI, 93.9% to 100%) and 78.6% (95% CI, 51.0% to 93.6%), respectively.

Prevalence, Genotyping of Escherichia coli and Pseudomonas aeruginosa Clinical Isolates for Oxacillinase Resistance and Mapping Susceptibility Behaviour

In the present study, multi-drug resistant isolates of Escherichia coli and Pseudomonas aeruginosa were obtained from different clinical specimens and were subjected to molecular typing to detect the genes encoding oxacillinases in these isolates. Subsequently, antibacterial activity of drugs was tested against selected clinical isolates. Two hundred ninety six isolates including 98 of E. coli and 148 of P. aeruginosa were collected from clinical specimens of different centers across India. Out of 246, 123 isolates showed weak synergy for ceftazidime or cefepime and imipenem or clavulanate and were considered as oxacillinase producers. Polymerase chain reaction (PCR) was performed to identify the variants of oxacillinases genes. Our results show a great diversity of occurance of oxacillinase (OXA) genes among clinical isolates. OXA-48 and OXA-10 was more prevalent in both E. coli (32.6% OXA-48; 16.3% OXA-10) and P. aeruginosa (OXA-48 32.4%; 27.0%) as evident by PCR. The incidence of other OXA genes in E. coli and P. aeruginosa varied from 4.0 to 12.1%. Of the tested drugs, cefepime plus sulbactam was found to be the most efficacious antibacterial agents with 86.5 to 87.8% susceptibility. Cefepime plus tazobactam was second most active antibacterial agent with 72.2 to 73.5% susceptibility. Surprisingly, imipenem plus cilastatin showed susceptibility to less than 35% isolates. From the above results, it is evident that cefepime plus sulbactam has enhanced in vitro antibacterial activity compared to cefepime and imipenem plus cilastatin and tazobactam combination in oxacillinases. One significant finding of this study was that cefepime was found to be effective only against the isolates caring OXA-1 and OXA-2 but found to be resistant to OXA-10, OXA-23, OXA-24, OXA-48, OXA-51 and OXA-58 genes; whereas cefepime in combination with sulbactam was found to be the most effective against all of these OXA genes in comparison to tazobactam combination.

Detection of β -Lactamases and Outer Membrane Porins among Klebsiella pneumoniae Strains Isolated in Iran.

This descriptive study was accomplished on 83 K. pneumoniae strains isolated from two hospitals in Tehran, Iran. Antibiotic susceptibility tests were performed by disc diffusion and broth microdilution methods. ESBLs, MBL, Amp-C, and KPC producing strains were detected by phenotypic confirmatory test, combination disk diffusion test (CDDT), Amp-C detection kit, and modified Hodge test, respectively. OXA-48, NDM-1, and CTX-M-15 genes were detected by PCR and sequencing methods. The outer membrane porins such as OmpK35 and OmpK36 were analysed by SDS-PAGE, PCR, and sequencing methods. From 83 K. pneumoniae isolates, 48 (57.5%), 3 (3.5%), 23 (28%), and 5 (6%) were ESBL, MBL, Amp-C, and KPC positive, respectively. The CTX-M-15 gene was detected in 30 (62.5%) and OXA-48 gene was found in 2 (4.1%) of the 48 ESBL-producing isolates. Two isolates harboured both OXA-48 and CTX-M-15; NDM-1 gene was not detected in this study. Outer membrane porin, OmpK35, was detected in 30 (62.5%) of 48 ESBL-producing isolates while OmpK36 was found in 35 (72.91%) of 48 ESBL-producing isolates. In this study, fosfomycin and tigecycline were more effective than other antibiotics. The high prevalence of β-lactamase-producing K. pneumoniae detected in this study is of great concern, which requires infection control measures including antibacterial management and identification of β-lactamases-producing isolates.

Detection of carbapenemase-producing enterobacteriaceae in the baltic countries and st. Petersburg area.

The spread of carbapenemase-producing Enterobacteriaceae is a global problem; however, no exact data on the epidemiology of carbapenemase in the Baltic countries and St. Petersburg area is available. We aimed to evaluate the epidemiology of carbapenemase-producing Escherichia coli and Klebsiella pneumoniae in the Baltic States and St. Petersburg, Russia, and to compare the different methods for carbapenemase detection. From January to May 2012, all K. pneumoniae (n = 1983) and E. coli (n = 7774) clinical isolates from 20 institutions in Estonia, Latvia, Lithuania, and St. Petersburg, Russia were screened for carbapenem susceptibility. The IMP, VIM, GIM, NDM, KPC, and OXA-48 genes were detected using real-time PCR and the ability to hydrolyze ertapenem was determined using MALDI-TOF MS. Seventy-seven strains were found to be carbapenem nonsusceptible. From these, 15 K. pneumoniae strains hydrolyzed ertapenem and carried the bla NDM gene. All of these strains carried integron 1 and most carried integron 3 as well as genes of the CTX-M-1 group. No carbapenemase-producing E. coli or K. pneumoniae strains were found in Estonia, Latvia, or Lithuania; however, NDM-positive K. pneumoniae was present in the hospital in St. Petersburg, Russia. A MALDI-TOF MS-based assay is a suitable and cost-effective method for the initial confirmation of carbapenemase production.

Detection of the frequency of PER-1 type extended-spectrum β-lactamase-producing Acinetobacter baumannii clinical isolates in Turkey: a multicenter study.

β-Lactamases are an important resistance mechanism in Acinetobacter baumannii. Pseudomonas extended-resistance (PER-1) type β-lactamase-producing strains have been reported from various geographic locations; however, PER-1 type β-lactamases from Turkish hospitals have not been investigated extensively. The aim of this study was to determine the prevalence of PER-1 type β-lactamases in A. baumannii isolates in various regions of Turkey. A total of 763 clinical A. baumannii isolates were collected from 9 university hospitals and 2 state hospitals between 2008 and 2011. Molecular amplification of the OXA-51 gene from the A. baumannii genome was performed in order to verify identification of the species. Real-time polymerase chain reaction was used to detect blaPER-1 genes. PER-1 was detected in 24.6% of the isolates. The annual frequencies of the PER-1 enzyme were detected as 52.2%, 35.9%, and 8.3% in 2008, 2009, and 2010, respectively. PER-1 prevalence decreased gradually over time. The differences observed in PER-1 prevalence among the regions of Turkey were statistically significant (chi-square test; P < 0.001). These data demonstrate that the frequency of detection of PER-1 type β-lactamases in A. baumannii species has decreased in Turkey. However, the increased carbapenem resistance, together with multidrug resistance, has created a worrisome situation regarding this pathogen.

Sub-Typing of Extended-Spectrum-β-Lactamase-Producing Isolates from a Nosocomial Outbreak: Application of a 10-Loci Generic Escherichia coli Multi-Locus Variable Number Tandem Repeat Analysis

Extended-spectrum β-lactamase producing Escherichia coli (ESBL-E. coli) were isolated from infants hospitalized in a neonatal, post-surgery ward during a four-month-long nosocomial outbreak and six-month follow-up period. A multi-locus variable number tandem repeat analysis (MLVA), using 10 loci (GECM-10), for ‘generic’ (i.e., non-STEC) E. coli was applied for sub-species-level (i.e., sub-typing) delineation and characterization of the bacterial isolates. Ten distinct GECM-10 types were detected among 50 isolates, correlating with the types defined by pulsed-field gel electrophoresis (PFGE), which is recognized to be the ‘gold-standard’ method for clinical epidemiological analyses. Multi-locus sequence typing (MLST), multiplex PCR genotyping of bla CTX-M, bla TEM, bla OXA and bla SHV genes and antibiotic resistance profiling, as well as a PCR assay specific for detecting isolates of the pandemic O25b-ST131 strain, further characterized the outbreak isolates. Two clusters of isolates with distinct GECM-10 types (G06-04 and G07-02), corresponding to two major PFGE types and the MLST-based sequence types (STs) 131 and 1444, respectively, were confirmed to be responsible for the outbreak. The application of GECM-10 sub-typing provided reliable, rapid and cost-effective epidemiological characterizations of the ESBL-producing isolates from a nosocomial outbreak that correlated with and may be used to replace the laborious PFGE protocol for analyzing generic E. coli.

English

This study aimed to investigate the existence and molecular epidemiological characteristics of&nbsp; multi-drug resistant Acinetobacter baumannii (MDRAB)-related resistance genes isolated from our hospital. Microdilution and disk diffusion methods were used to detect the antibiotic susceptibility of 46 MDRAB isolates that carried OXA-51 gene. Pulsed-field gel electrophoresis (PFGE) was used to analyze the homologies among the strains. Resistance genes were tested through polymerase chain reaction. Among the 46 MDRABA, a total of nine, isolates were categorized as strain A (19.6%), eight as strain B (17.4%), and four as strain O (8.7%). A total of 41 isolates (89.1%) carried the OXA23 gene, 17 (37.0%) carried the PER gene, and six (13%) carried the IMP gene. Six strains (13%) did not carry the membrane pore protein gene carO. The numbers of isolates that carried a particular gene were as follows: 40 (87.0%), armA; 41 (89.1%), ant(3&rdquo;)-I; 33 (71.7%), aac(3)-I; 2 (4.3%), aac(3)-II; 1 (2.2%), aac(6&rsquo;)-II; and 1 (2.2%) and aph(3&rsquo;)-VI. Most of the isolates (93.5%) carried the qacE∆1 gene. These hospital MDRAB isolates were proven to simultaneously carry a variety of drug resistance genes. Strains A and B were the&nbsp;major&nbsp;epidemic strains of nosocomial&nbsp;MDRAB. Key words: Acinetobacter baumannii, resistance gene, pulsed-field gel electrophoresis, multi-drug resistant.

Comparison between phenotypic and PCR for detection of OXA-23 type and metallo-beta-lactamases producer Acinetobacter spp.

Background: Resistance to carbapenems is developing around the world and can cause many problems for treatment of patients. Production of metallo-beta-lactamase (MBL) is one of the main mechanism for this type of resistance. So, detection of MBL-producer microorganisms can prevent the spread of this type of resistance.Materials and methods: In this study 94 Acinetobacter spp. were investigated. Resistance to imipenem was conducted after purification and identification. Combination disc (CD) and Double Disc Synergy Test (DDST) were performed for phenotypic detection of MBL and the molecular PCR method was done for vim-1, vim-2, imp-1 and OXA-23 genes.Results: According to TSI, SIM and oxidation-fermentation (OF) test and PCR assay 93 Acinetobacter baumannii and one strain Acinetobacter lwoffii were identified. 85% of them were resistant to imipenem. 34% of them have a positive combination disc test (CD) while Double Disc Synergy Test (DDST) was negative for all of them. The vim-1, vim-2 and imp-1 genes were not detected in PCR molecular method, however in 74% of strains with positive results in combination disc, were positive for the OXA-23 gene after PCR test. This study shows that the blaOXA-23 resistance determinant may become an emerging therapeutic problem.Discussion: According to the results, it seems that combination disc does not have enough specificity for detection of MBL-producer Acinetobacter and using Double Disc Synergy Test (DDST) can be more convenient.

Distribution of OXA-Type Class D β-Lactamase Genes Among Nosocomial Multi Drug Resistant Acinetobacter baumannii Isolated in Tehran Hospitals

Background: Multiple drug-resistant strains of Acinetobacter have become common in hospitals worldwide. The problem becomes more acute with increasing resistance to carbapenems, the last resort in the treatment of hospital acquired Acinetobacter baumannii infections. Objectives: The current study was conducted to determine the antimicrobial susceptibility patterns and prevalence of OXA-type carbapenemases, among clinical isolates of A. baumannii, in Tehran hospitals, Iran. Materials and Methods: Isolates were identified as A. baumannii by PCR with specific primers for bla OXA-51-like gene. Their susceptibilities to different antibiotics were determined using disk diffusion method. Isolates were then subjected to multiplex-PCR targeting bla oxa-51, bla oxa-24, blaoxa-23 and bla oxa-58 genes. Results: Results showed that 123 of 131 (93.89%) Acinetobacter species, possessed bla oxa-51-like gene and were identified as A.baumannii. 54.47% of isolates were resistant to amikacin, 67.47% resistant to imipenem and 84.55% resistant to meropenem. All isolates were susceptible to colistin and polymixin B. 43 of 123 A. baumannii isolates (34.95%) were MDR. These isolates were resistant to amikacin, ciprofloxacin, imipenem, cefrazidim. Among 123 isolates, 100(81.3 %) had an acquired oxa-23like carbapenemase 10 (8.1%) possessed oxa-24-like, and 1 (0.81%) possessed oxa-58-like carbapenemase. Conclusions: The present study showed that bla OXA-23-like was the most frequent carbapenemase identified among carbapenem-resistant A. baumannii isolated in Tehran hospitals. Evaluation of antibiotic resistance genes in A. baumannii, is necessary to control further dissemination of these antibiotic resistant genes.

Complete Genome Analysis of Three Acinetobacter baumannii Clinical Isolates in China for Insight into the Diversification of Drug Resistance Elements

BackgroundThe emergence and rapid spreading of multidrug-resistant Acinetobacter baumannii strains has become a major health threat worldwide. To better understand the genetic recombination related with the acquisition of drug-resistant elements during bacterial infection, we performed complete genome analysis on three newly isolated multidrug-resistant A. baumannii strains from Beijing using next-generation sequencing technology.Methodologies/Principal FindingsWhole genome comparison revealed that all 3 strains share some common drug resistant elements including carbapenem-resistant bla OXA-23 and tetracycline (tet) resistance islands, but the genome structures are diversified among strains. Various genomic islands intersperse on the genome with transposons and insertions, reflecting the recombination flexibility during the acquisition of the resistant elements. The blood-isolated BJAB07104 and ascites-isolated BJAB0868 exhibit high similarity on their genome structure with most of the global clone II strains, suggesting these two strains belong to the dominant outbreak strains prevalent worldwide. A large resistance island (RI) of about 121-kb, carrying a cluster of resistance-related genes, was inserted into the ATPase gene on BJAB07104 and BJAB0868 genomes. A 78-kb insertion element carrying tra-locus and bla OXA-23 island, can be either inserted into one of the tniB gene in the 121-kb RI on the chromosome, or transformed to conjugative plasmid in the two BJAB strains. The third strains of this study, BJAB0715, which was isolated from spinal fluid, exhibit much more divergence compared with above two strains. It harbors multiple drug-resistance elements including a truncated AbaR-22-like RI on its genome. One of the unique features of this strain is that it carries both bla OXA-23 and bla OXA-58 genes on its genome. Besides, an Acinetobacter lwoffii adeABC efflux element was found inserted into the ATPase position in BJAB0715.ConclusionsOur comparative analysis on currently completed Acinetobacter baumannii genomes revealed extensive and dynamic genome organizations, which may facilitate the bacteria to acquire drug-resistance elements into their genomes.

Probe ligation and real-time detection of KPC, OXA-48, VIM, IMP, and NDM carbapenemase genes

The Check-MDR Carba test (Check-Points, Wageningen, Netherlands), which is based on specific molecular recognition of blaNDM, blaKPC, blaOXA-48, blaVIM, and blaIMP genes by DNA probe ligation and real-time PCR detection, was evaluated on 183 well-characterized Gram-negative rods. Representatives of the 5 gene families were accurately identified (specificities and sensitivities of 100%) within 4.5 hours. This test may be helpful to differentiate carbapenem resistance mediated by carbapenemases from those involving other mechanisms.

First Identification of Novel NDM Carbapenemase, NDM-7, in Escherichia coli in France

BackgroundThe NDM-1 carbapenemase has been identified in 2008 in Enterobacteriaceae. Since then, several reports have emphasized its rapid dissemination throughout the world. The spread of NDM carbapenemases involve several bla NDM gene variants associated with various plasmids among several Gram negative species.MethodologyA multidrug-resistant E. coli isolate recovered from urine of a patient who had travelled to Burma has been characterized genetically and biochemically.Principal Findings E. coli COU was resistant to all antibiotics tested except amikacin, tigecycline, fosfomycin, and chloramphenicol. Analysis of the antibiotic resistance traits identified a metallo-ß-lactamase, a novel NDM variant, NDM-7. It differs from NDM-4 by a single amino acid substitution sharing an identical extended spectrum profile towards carbapenems. The bla NDM-7 gene was located on an untypeable conjugative plasmid and associated with a close genetic background similar to those described among the bla NDM-1 genes. The isolate also harbours bla CTXM-15 and bla OXA-1 genes and belonged to ST167.SignificanceThis study highlights that spread of NDM producers correspond to spread of multiple bla NDM genes and clones and therefore will be difficult to control.