Resistance Mechanism And Virulence Study Of ST11 Non-K1/K2 Capsular Serotype Hypervirulent Klebsiella Pneumoniae

Objective:K.pneumoniae is one of the important pathogenic bacteria that causes community acquired and hospital acquired infections,usually are refractory infections.Nowadays,lots of researches are concerning on the separation and resistance of K.pneumoniae,but rarely about the new high virulence K.pneumoniae which also carries resistance genes.This research is mainly for analyzing the virulence and resistance mechanisms of carbapenem-resistant hyper-virulent K.pneumoniae which isolated from the Second Affiliated Hospital of Zhejiang University.Methods:The carbapenem-resistant K.pneumoniae was isolated from blood culture sample of a patient died of infectious shock in Second Affiliated Hospital of Zhejiang University;Identification was conducted by vitek 2 compact automatic microbial analysis system;Antimicrobial susceptibility was determined by agar dilution method;String test was used for detection of hypermucoviscous phenotype,PCR was performed for determination of capsular serotypes and virulence genes with specific primers,and Galleria mellonella was used for evaluation of virulence;Conjugation experiment,amplification of resistance genes(including blaKPC-2,blaTEM,,blaSHV,blaCTX-M)together with sequcing were perfoemed to investigate the mechanism of drug-resistance;Homological analysis was detected by Pulsed-field gel electrophoresis(PFGE)and Multi Locus Sequence Typing(MLST).Results:The isolate was positive for sting test,and none of K1/K2/K54/K57/K20 capsular serotypes,it was also positive for several virulence factors including fimH-1,mrkD,kpn,entB,iutA,irp-1,irp-2,ycfM,fyuA,ybts,Trat,and confirmed as hypervirulent K.pneumoniae by G.mellonella infection model,1,4 strains showed high virulence and 2,3,7 strains showed medium toxicity;The isolate was resistant to carbapenem and cephalosporin,carrying blaKPC-2,blaTEM-1 and blaCTX-M-65,all of which could be transferred to transconjugants by conjugation assay;MLST analysis identified the isolate as ST11.Conclusions:The ST11 Non-K1/K2 capsular serotype hypervirulent K.pneumoniae which produced KPC-2-type carbapenemase was associated with high pathogenicity,leading to high mortality.The coexistence of virulence and resistance genes challenges in the battle against infections.