ABSTRACT
Objective:To investigate the antimicrobial resistance characteristics of carbapenem-resistant Enterobacteriaceae （CRE） isolated from outpatients with diarrhea in Shanghai， and provide support for surveillance， prevention and control of CRE. Methods:A total of 800 fecal swabs of the outpatients with diarrhea were collected from 23 sentinel hospitals for diarrhea pathogen surveillance in Shanghai from January 2018 to December 2019. The drug-resistant strains were isolated using MacConkey plates containing 1 μg/μL meropenem. The collected strains were identified preliminarily by the VITEK-2 Compact system and VITEK mass spectrometry. The minimum inhibitory concentration （MIC） of the strain was determined by the broth microdilution method. The multi-locus sequence typing （MLST） method and pulsed-field gel electrophoresis （PFGE） were used to analyze the homology of drug-resistant strains. The transferability of the resistance gene was investigated by a junction experiment. High-throughput sequencing was used to characterize the isolates. Results:Seven non-repetitive CRE isolates were multi-drug resistant carbapenem-resistant Escherichia coli （CREC） strains that produce New Delhi metallo-β-lactamase （NDM） with resistance to several commonly used antibiotics in clinical therapy. The molecular typing results showed that the CRE strains had different sequence types， and diverse PFGE patterns. The stains were all positive for blaNDM genes， including blaNDM-5 and blaNDM-13， with blaNDM-5 as the main type. The carbapenem-resistant genes could be transferred to EC600 by conjugation. Conclusion:The intestinal carbapenem-resistant strains in this study are all NDM-producing Escherichia coli. The isolates carried blaNDM and other resistance genes. The MLST analysis showed that they belonged to different cloning types. Antimicrobial resistance genes could be horizontally transferred to EC600 by conjugation.
ABSTRACT
Objective To investigate the detection of IMP andVIM metallo-β-lactamases (MβLs)genes in clinically iso-lated gram-negative bacteria as well as bacterial resistance toβ-lactam antimicrobial agents.Methods 113 clinically isolated bacteria were performed antimicrobial susceptibility testing by Kirby-Bauer method ,drug-resistant genes IMP and VIM were detected by polymerase chain reaction (PCR),PCR products were sequenced and aligned with BLAST software. Results VIM gene was detected in 1 Pseudomonas fluorescens strain ,IMP gene was detected in 15 strains ,they were Klebsiella pneumoniae (n=6),Acinetobacter baumannii (n=3),Escherichia coli (n=2),Ralstonia picket-tii (n=1),Pseudomonas aeruginosa (n=1 ),Citrobacter amalonaticua (n=1 ),and Enterobacter cloacae (n=1 ). BLAST results showed that VIM gene was VIM-2 subtype,similarity with gene bank was 99%;all IMP genes were IMP-1 subtype,which were highly homologous ,similarity was 98%-99%.Resistant rates of IMP positive strains to ceftriaxone,cefotaxime,cefoxitin,aztreonam and imipenem were all significantly higher than negative strains (all P <0.05).Conclusion IMP genes of different strains are highly homologous,all are IMP-1 type,indi-cating that IMP genes are highly transmissible and can spread among different species of bacteria.IMP genes are related with resistance ofβ-lactam antimicrobial agents.