Relationship between virulence and carbapenem resistance phenotype of Klebsiella pneumoniae from blood infection:identification of a carbapenem-resistant and hypervirulent strain
Objective:To investigate the relationship between the virulence and the carbapenem resistance phenotype of Klebsiella pneumoniae from blood infection,and to identify carbapenem-resistant and hypervirulent Klebsiella pneumoniae(CR-HVKP)strains.Methods:A total of 192 Klebsiella pneumoniae strains were isolated from blood culture of patients with bloodstream infections from 2016 to 2019,of which 96 isolates were carbapenem-resistant Klebsiella pneumoniae(CRKP)and 96 were carbapenem-sensitive Klebsiella pneumoniae(CSKP).The drug susceptibility was detected by VITEK-2 automatic microbial analyzer;carbapenemase genes,virulence genes and capsule typing were detected by polymerase chain reaction;the high viscosity phenotype of strains was detected by string test,and the genome characteristics of CR-HVKP were detected by whole genome sequencing.Serum killing and biofilm formation test were used to further verify the virulence of CR-HVKP.Results:There were significant differences in drug resistance to common antibiotics,except for minocycline between CSKP and CRKP isolates(all P<0.05).92 out of 96 CRKP isolates carried carbapenemase genes,mainly blaKPC-2.The string tests were positive in 4 isolates of CRKP and 36 isolates of CSKP(P<0.05).The detection rates of virulence genes Kfu,aerobictin,iutA,ybtS,rmpA,magA,allS,and capsule antigen K1 and K2 in CSKP group were significantly higher than those in CRKP group(all P<0.05).One HVKP strain was detected in the CRKP group(CR-HVKP)and 36 HVKP was detected in the CSKP group(P<0.05).The CR-HVKP strain belonged to the MLST412,serotype K57,expressed iutA,entB,mrkD,fimH,and rmpA virulence genes,and showed strong biofilm formation and significantly increased serum resistance.Whole genome sequencing results showed that this CR-HVKP isolate carried blaSHV-145,blaTEM-1,blaCTX-M-3,fosA6,oqxA5,oqxB26,and aac(3)-Ⅱd resistance genes,accompanied by abnormalities in outer membrane protein K(OmpK)35 and OmpK36.Conclusions:The drug resistance of CRKP is significantly higher than that of CSKP,while CRKP carrying fewer virulence genes in both number and types compared to CSKP.A new MLST type of carbapenem-resistant and hypervirulent Klebsiella pneumoniae strain has been detected,which requires clinical awareness and epidemiological monitoring.
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