Investigation Of Carbapenem Resistance Mechanisms In Clinical Isolates Of BlaNDM-1in Klebsiella Pneumoniae

Objective:The aim of this study is to investigate the resistance mechanisms, molecularcharacteristics and prevalence of blaNDM-1in Klebsiella pneumoniae clinicalisolates from Nanchang several hospitals.Methods:Identified by Vitek-32automated microbial identified.Antimicrobial susceptib-ility testing was determined by disc agar diffusion method and confirmed by E-test.β-lactamases (AmpC, KPC) were screened by three dimensional test. Metallo-beta-lactamase was determined by EDTA-disk synergy test. TEM、SHV、CTX-M-1、CTX-M-9、KPC-1、KPC-2、GES、IMP-1、IMP-2、VIM-1、VIM-2、SPM-1、DHA、CMY、ompK35、ompK36and NDM-1were detected by PCR,and the positvesamples’genotypes were confirmed by DNA sequencing.Molecular typing wasdetermined by Multi-locus sequence typing (MLST) and Pulsed-field gel electroph-oresis (PFGE).Conjugation experiments and transformation test were performed toconfirm whether the NDM-1gene was located on plasmid．Results:Various clinical departments samples which were collected from January2011to June2012in Nanchang,27Klebsiella pneumoniae isolates were resistant tocarbapenem,Two carbapenem-resistant Klebsiella pneumoniae isolates (KP12andKP18) were found to harbor blaNDM-1,In addition to blaNDM-1, NC12also carriedblaSHV-1, while NC18harbored additional resistance genes, including blaSHV-12,armA,blaCTX-M-14and blaTEM-1. NC12and NC18belonged to ST15and novelST1031.PFGE revealed that the2isolates belonged to different PFGE clusters.Asexpected, resistance plasmids carrying blaNDM-1for KP12were successfullytransferred into the recipient E. coli J53through conjugation. Interestingly, transferof resistance plasmids for KP18to recipients was not successful using filter mating conjugation.In contrast, resistance plasmids for both NC12and NC18could betransferred into the recipient (E. coli DH5α) using chemical transformation.Conclusions:This is the first report of blaNDM-1expression by Klebsiella pneumoniaeclinical isolates in mainland, China, indicating that blaNDM-1is disseminated amongEnterobacteriaceae in China. Majority of the blaNDM-1genes were located on thesame plasmids，indicating that similar plasmids disseminated.The patients not initiallyhave reached these countries from the Indian subcontinent or other countries.