ABSTRACT
Objective To investigate the distribution of common carbapenem resistance genes and virulence genes in and understand the molecular epidemiology of carbapenem-resistant Klebsiella pneumoniae (CRKP) strains.Methods A total of 84 non-duplicate CRKP isolates were collected from Renji Hospital,Shanghai Jiao Tong University School of Medicine and Changzheng Hospital,the Second Military Medical University,in 2015.Kirby-Bauer disk diffusion method was used to test their susceptibility to 15 antimicrobial agents.The HM phenotype of K.pneumoniae was determined by string test.Carbapenem-resistant genes and virulence genes were detected by polymerase chain reaction (PCR).The molecular epidemiology of the 84 isolates were further analyzed by multi locus sequence typing (MLST).The population structure of CRKPs was evaluated by eBURST with the results of MLST.Results Antimicrobial susceptibility test showed that 84 isolates were highly resistant to most antimicrobial agents such as carbapenems,penicillins,cephalosporins and aztreonam.More than 90％ of the strains were resistant to most of the antibiotics tested except ciprofloxacin (77.4％,65/84) and amikacin (82.1％,69/84).Two strains showed HM phenotype.PCR results showed that 90.5％ (76/84) of the strains were positive for blaKPC-2,1.2％ (1/84) positive for blaNDM and blaIMP each,but either blaOXA or blaVIM was not identified.The overall prevalence of virulence genes was low except for mrkD (97.6％,82/84),ybtS (92.9％,78/84) and entB (100％,84/84).Eight sequence types (STs) were obtained.The dominant clone was ST11 (84.5％,71/84),and the two strains of HM phenotype were ST11.eBURST analysis identified 2 ST groups among the 84 CRKPs.Each ST group includes 2 ST types (ST11 and ST1869,ST15 and ST709),respectively.The other four ST types were single ST type.In this study,71 strains of ST11,4 ST15 and 4 ST323 belonged to CC258,CC15 and CC163 clones,respectively.Conclusions CRKP is highly resistant to the commonly used antibiotics.The multidrug resistance or pandrug-resistance of K.pneumoniae is mainly associated with the expression of blaKPC-2 gene.Three virulence genes mrkD,ybtS and entB are highly prevalent in the CRKP isolates.The dominant clone of KPC-producing K.pneumoniae is ST11 in both hospitals.