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Objecive To investigate the prevalence of NDM-type carbapenemases in the carbapenem-resistant Escherichia coli strains collected from Ruijin Hospital, Shanghai Jiaotong University School of Medicine. The epidemiological characteristics of NDM-type carbapenemase-producing isolates were analyzed.Methods Eighteen strains were collected from November 2013 to January 2015 in the clinical microbiology laboratory of Ruijin Hospital. All of them were resistant to imipenem or meropenem (inhibition zone diameter≤19 mm). The blaNDM gene was detected by PCR. The amplified products were subjected to sequencing analysis. Conjugation experiment was carried out to verify the transferability of plasmids. Multilocus sequence typing (MLST) and pulsed field gel electrophoresis (PFGE) were performed to analyze the molecular epidemiology.Results The blaNDM gene was identified in 6 strains, 4 of which had blaNDM-1-type and 2 had blaNDM-5-type carbapenemase gene. Three strains were positive in the conjugation experiment. MLST analysis showed that 6 NDM carbapenemase-producing isolates belonged to ifve sequence types, corresponding to five PFGE-DNA patterns (A-E). Two of these isolates shared the identical sequence type (ST5018) and nearly the same PFGE-DNA patterns (A1, A2).Conclusions NDM-type carbapenemase-producing E. coli is identified in this study. Most blaNDM-positive cases were sporadic. Plasmid might play an important role in the spread of blaNDM inE. coli. The blaNDM-5 type carbapenemase gene was first identified in Shanghai, to which more attention should be paid.
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BACKGROUND: Rapid detection of carbapenemase-producing gram-negative bacilli (GNB) is required for optimal treatment of infected patients. We developed and assessed a new disk carbapenemase test (DCT). METHODS: Paper disks containing 0.3 mg of imipenem and bromothymol blue indicator were developed, and the performance of the DCT were evaluated by using 742 strains of GNB with or without carbapenemases. RESULTS: The paper disks were simple to prepare, and the dried disks were stable at -20℃ and at 4℃. The DCT detected 212 of 215 strains (98.6% sensitivity with 95% confidence interval [CI] 96.0-99.5%) of GNB with known class A (KPC and Sme) and class B (NDM, IMP, VIM, and SIM) carbapenemases within 60 min, but failed to detect GES-5 carbapenemase. The DCT also detected all two Escherichia coli isolates with OXA-48, but failed to detect GNB with OXA-232, and other OXA carbapenemases. The DCT showed 100% specificity (95% CI, 99.2-100%) in the test of 448 imipenem-nonsusceptible, but carbapenemase genes not tested, clinical isolates of GNB. CONCLUSIONS: The DCT is simple and can be easily performed, even in small laboratories, for the rapid detection of GNB with KPC, NDM and the majority of IMP, VIM, and SIM carbapenemases.