Project description:BackgroundCarbapenemase producing Enterobacteriaceae are becoming a major public health concern globally, however, relatively little is known about the molecular and clinical epidemiology of these organisms in many parts of the world.MethodsAs part of a laboratory surveillance programme, 96 carbapenem non-susceptible Enterobacteriaceae isolates from clinical samples from patients in seven hospitals were referred for investigation for carbapenemases. Using polymerase chain reaction (PCR) to screen for a collection of genes encoding carbapenemases, 33 of 96 (34.5%) isolates were confirmed as carbapenemase producers. NDM-1 producers were the most prevalent at 64% (21/33) whilst OXA-181 was the second most common carbapenemase constituting 24.5% (8/33) of the carbapenemase producing isolates. Seven of these eight OXA-181 positive isolates underwent further characterisation with screening for other transmissible antimicrobial resistance determinants using PCR. Clonal relatedness was explored using Multilocus sequence typing (MLST) and Pulsed Field Gel Electrophoresis (PFGE). Plasmid characterisation was performed including restriction analysis and transfer by conjugation or transformation.ResultsIn addition to the OXA-181 gene, all contained other transmissible resistance determinants including extended spectrum β-lactamases, oxacillinases or 16S rRNA methylase genes, but none contained metallo-β-lactamases or serine carbapenemases. All isolates had a multidrug resistant phenotype with two isolates being resistant to every antibiotic tested including colistin. Multilocus sequence typing confirmed five isolates belonged to ST17 and two to ST14, with those belonging to the same sequence type having identical PFGE profiles. The OXA-181 gene was typically carried on large plasmids which were mostly non-conjugative.ConclusionsOXA-181 carbapenemase appears to be an important and probably under-recognised cause of carbapenem resistance in Enterobacteriaceae in Singapore. Further coordinated research into clinical and molecular epidemiology of carbapenemases is urgently required in Singapore and throughout Asia.

Project description:Background and Objective:The emergence of carbapenem-resistant K. pneumoniae (CRKP) continues to escalate and is alarming because of the emergence of pan drug-resistant strains. The objective of this study was to investigate the existence of 12 carbapenemase genes among CRKP clinical isolates. Methods:Ninety-six Klebsiella spp. clinical isolates were collected. The isolates were identified phenotypically and genotypically. These isolates were screened for susceptibility to 24 different antibiotics. The modified Hodge test (MHT) and the Carba Nordmann/Poirel (NP) test were used to phenotypically screen carbapenem-resistant strains for carbapenemase production. Phenotypic characterization of carbapenemases was performed using the combined disk synergy test (CDST). Additionally, the presence of 12 carbapenemase genes in CRKP isolates was investigated. The DNA sequence of bla NDM and bla GES genes was determined. The BOX-PCR technique was used to determine the clonal relationship between CRKP isolates. Results:All carbapenem-resistant isolates were related to K. pneumoniae. Susceptibility testing showed that 19.79% (19/96) of the collected isolates were carbapenem-resistant. Of the CRKP isolates, 68.42% (13/19) tested positive for the MHT and Carba NP test. CDST showed that 42.11% (8/19), 63.16% (12/19), 47.37% (9/19), and 73.68% (14/19) of the CRKP isolates tested positive for the inhibitory effect of clavulanic acid, sulbactam, phenylboronic acid, and tazobactam, respectively, while 84.21% (16/19) and 68.42% (13/16) tested positive for the inhibitory effect of EDTA and mercaptopropionic acid, respectively. It was found that 10.53% (2/19) of the isolates tested positive for the inhibitory effect of sodium chloride. Molecular investigation of carbapenemases showed that 26.32% (5/19), 73.68% (14/19), 21.05% (4/19), 10.53% (2/19), and 5.26% (1/19) of the isolates tested positive for bla NDM, bla OXA-48, bla OXA-181, bla OXA-51, and bla OXA-23, respectively. None of the isolates tested positive for bla OXA-40 and bla OXA-58. Two allelic variants of bla NDM (bla NDM-1 and bla NDM-25) were detected. BOX-PCR revealed high clonal relatedness between CRKP isolates. Conclusion:MHT was more sensitive than Carba NP test for evaluating carbapenemase production and class D carbapenemase genes were the most prevalent of the 12 carbapenemase genes that were evaluated.

Project description:IncX3 and IncL plasmids have been named as catalysts advancing dissemination of blaOXA-181 and blaOXA-48 genes. However, their impact on the performance of host cells is vastly understudied. Genetic characteristics of blaOXA-48- and blaOXA-181-containing Klebsiella pneumoniae (EFN299), Klebsiella quasipneumoniae (EFN262), and Enterobacter cloacae (EFN743) isolated from clinical samples in a Ghanaian hospital were investigated by whole-genome sequencing. Transfer of plasmids by conjugation and electroporation, plasmid stability, fitness cost, and genetic context of blaOXA-48, blaOXA-181, and blaDHA-1 were assessed. blaOXA-181 was carried on two IncX3 plasmids, an intact 51.5-kb IncX3 plasmid (p262-OXA-181) and a 45.3-kb IncX3 plasmid (p743-OXA-181) without replication protein sequence. The fluoroquinolone-resistant gene qnrS1 region was also excised, and unlike in p262-OXA-181, the blaOXA-181 drug-resistant region was not found on a composite transposon. blaOXA-48 was carried on a 74.6-kb conjugative IncL plasmid with unknown ~10.9-kb sequence insertion. This IncL plasmid proved to be highly transferable, with a conjugation efficiency of 1.8 × 10-2. blaDHA-1 was present on an untypeable 22.2 kb genetic structure. Plasmid stability test revealed plasmid loss rate between 4.3% and 12.4%. The results also demonstrated that carriage of IncX3-blaOXA-181 or IncL-blaOXA-48 plasmids was not associated with any fitness defect, but rather an enhanced competitive ability of host cells. This study underscores the significant contribution of IncX3 and IncL plasmids in the dissemination of resistance genes and their efficient transfer calls for regular monitoring to control the expansion of resistant strains. IMPORTANCE The growing rate of antibiotic resistance is an important global health threat. This threat is exacerbated by the lack of safe and potent alternatives to carbapenems in addition to the slow developmental process of newer and effective antibiotics. Infections by carbapenem-resistant Gram-negative bacteria are becoming almost untreatable, leading to poor clinical outcomes and high mortality rates. OXA-48-like carbapenemases are one of the most widespread carbapenemases accounting for resistance among Enterobacteriaecae. We characterized OXA-48- and OXA-181-producing Enterobacteriaecae to gain insights into the genetic basis and mechanism of resistance to carbapenems. Findings from the study showed that the genes encoding these enzymes were carried on highly transmissible plasmids, one of which had sequences absent in other similar plasmids. This implies that mobile genetic elements are important players in the dissemination of resistance genes. Further characterization of this plasmid is warranted to determine the role of this sequence in the spread of resistance genes.

Project description:BackgroundThe spread of carbapenemase-producing Enterobacteriaceae (CPE) is a great problem of healthcare worldwide. Study of the spread for bla OXA-48-like genes coding epidemically significant carbapenemases among hospital pathogens is important for the regional and global epidemiology of antimicrobial resistance.MethodsAntibacterial resistant isolates of Klebsiella pneumoniae (n = 95) from 54 patients, P. mirabilis (n = 32) from 20 patients, Enterobacter aerogenes (n = 6) from four patients, and Enterobacter cloacae (n = 4) from four patients were collected from January, 2013 to October, 2014 in neurosurgical intensive care unit (ICU) of the Burdenko Neurosurgery Institute, Moscow. Characteristics of the isolates were done using susceptibility tests, PCR detection of the resistance genes, genotyping, conjugation, DNA sequencing, and bioinformatic analysis.ResultsMajor strains under study were multi drug resistant (MDR), resistant to three or more functional classes of drugs simultaneously-98.9 % K. pneumoniae, 100 % P. mirabilis, one E. aerogenes isolate, and one E. cloacae isolate. Molecular-genetic mechanism of MDR in K. pneumoniae and P. mirabilis isolates were based on carrying of epidemic extended-spectrum beta-lactamase bla CTX-M-15 gene (87.2 and 90.6 % accordingly), carbapenemase bla OXA-48-like gene (55.3 and 23.3 % accordingly), and class 1 (54.8 and 31.3 % accordingly) and class 2 (90.6 % P. mirabilis) integrons. The bla OXA-48-like-positive K. pneumoniae were collected during whole two-year surveillance period, while P. mirabilis and Enterobacter spp. carrying bla OXA-48-like genes were detected only after four and 18 months after the research start, respectively. The bla OXA-48-like gene acquisition was shown for P. mirabilis isolates collected from five patients and for E. cloacae isolate collected from one patient during their stay in the ICU, presumably from bla OXA-48-like-positive K. pneumoniae. The source of the bla OXA-244 gene acquired by E. aerogenes isolates and the time of this event were not recognized.ConclusionsThe expanding of CPE in the surveyed ICU was associated with the spread of bla OXA-48 and bla OXA-244 carbapenemase genes documented not only among K. pneumoniae, well-known bacterial host for such genes, but among P. mirabilis, E. aerogenes, and E. cloacae.

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Bla(OXA-181)-positive Klebsiella pneumoniae, Singapore.

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bla(OXA-181)-positive Klebsiella pneumoniae, Singapore.

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