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.

Objective To investigate the clinical characteristics and molecular epidemiology of carbapenem-resistant Klebsiella pneumoniae(CRKP)isolated from patients with bloodstream infections in a large tertiary-care general hospital in Southwest China.Methods A total of 131 strains of non-repeating CRKP were collected from the blood cultures of patients who had bloodstream infections in 2015-2019.The strains were identified by VITEK-2,a fully automated microbial analyzer,and matrix-assisted laser desorption ionization-time of flight(MALDI-TOF)mass spectrometry.The minimum inhibitory concentration(MIC)was determined by microbroth dilution method.The common carbapenemase resistant genes and virulence factors were identified by PCR.Homology analysis was performed by multilocus sequencing typing.Whole genome sequencing was performed to analyze the genomic characteristics of CRKP without carbapenemase.Results The 131 strains of CRKP showed resistance to common antibiotics,except for polymyxin B(1.6%resistance rate)and tigacycline(8.0%resistance rate).A total of 105(80.2%)CRKP strains carried the Klebsiella pneumoniae carbapenemase(KPC)resistance gene,15(11.4%)strains carried the New Delhi Metallo-β-lactamase(NDM)gene,and 4(3.1%)isolates carried both KPC and NDM genes.Sequence typing(ST)11(74.0%)was the dominant sequence type.High detection rates for mrkD(96.2%),fimH(98.5%),entB(100%),and other virulence genes were reported.One hypervirulent CRKP strain was detected.The seven strains of CRKP that did not produce carbapenemase were shown to carry ESBL or AmpC genes and had anomalies in membrane porins OMPK35 and OMPK36,according to whole genome sequencing.Conclusion In a large-scale tertiary-care general hospital,CRKP mainly carries the KPC gene,has a high drug resistance rate to a variety of antibiotics,and possesses multiple virulence genes.Attention should be paid to CRKP strains with high virulence.