Analysis of drug resistance,virulence and biofilm formation ability in hypermucoviscous Klebsiella pneumoniae from raw milk

【Objective】To assess biofilm formation ability and risk of drug resistance and virulence of hypermucoviscous Klebsiella pneumoniae(hmKP)from raw milk and its environment,to propose a warning of potential risks posed by hmKP,so as to provide a theoretical basis for the appropriate prevention and control of Klebsiella pneumoniae(KP).【Method】Phenotypes of extended-spectrum β-lactamase(ESBLs)in 32 strains of hmKP were identified by drug sensitive slips method. Biofilm formation ability was detected by the semi-quantitative crystal violet method. Drug resistance genes and virulence genes carried by hm KP were detected through PCR.【Result】Twenty-four ESBLs-negative strains(non-ESBLs-KP,75.00%)and 8 ESBLs-positive strains(ESBLs-KP,25.00%)were identified from 32 hmKP strains,all of which could form biofilm,among which 10 had strong biofilm formation ability,17 had moderate biofilm formation ability,and 5 had weak biofilm formation ability. Among the 10 hm KP strains with strong biofilm formation ability,7 strains were from raw milk samples. Detection rate of ESBL-KP with strongly biofilm formation ability(37.50%)was higher than that of non-ESBL-producing strains(29.17%). All hm KP carried at least 4 kinds of drug resistance genes,and the sequence of drug resistance risk was tetracyclines = aminoglycosides > β-lactams > sulfonamides > quinolones > chloramphenicols,in which ESBLs-KP carried more than 8 kinds of drug resistance genes. 30 types of gene profiles were found in32 strains of hmKP,but no dominant drug resistance gene profiles were found. Five virulence genes including wabG,fimH,mrkD,entB and ybtS were detected in 32 hm KP strains. The detection rates of wabG,entB,fimH and mrkD was100.00%,followed by that of ybtS(21.88%). None of the strains carried iutA and rmpA genes. Two virulence gene profiles(fimH-mrkD-wabG-entB and fimH-mrkD-wabG-entB-ybtS)were found,and difference was whether they carried the ybtS gene. Although there was no significant difference in the detection rate of virulence genes between ESBLs-KP and non-ESBLs-KP(P>0.05),the detection rate of ybtS gene in ESBLs-KP was higher than that in non-ESBLs-KP.【Conclusion】hmKP from raw milk has a high risk of virulence and multiple drug resistance and is a major potential source of clinical KP infection. People are advised not to drink raw milk directly. Competent departments should strengthen the monitoring of drug resistance and virulence of hm KP in raw milk to grasp the distribution pattern of virulence,thus accurately preventing potential risk.