| BACKGROUND:Klebsiella pneumonae is one of the most important pathogens responsible for serious infections such as bacteremia,pneumonia,intra-abdominal infections and urinary tract infections.During the past two decades,a new variant termed hypervirulent K.pneumoniae(hvKP)has been reported in Asia,and this strain is emerging globally.Although the prevalence of hvKP is high in China,few studies have focused on bloodstream infections(BSIs)caused by hvKP strains.OBJECTIVE:The aim of this study was to systematically analyze the risk factors,molecular characteristics and patient mortality of hvKP induced BSIs.METHODS:Consecutive cases of K.pneumoniae BSIs between September 2015 and December 2016 were collected from patients hospitalized at Jinling Hospital.Only the first bacteremia episode for each patient was included in this retrospective study.A positive polymerase chain reaction(PCR)amplification of the regulator of mucoid phenotype A(rmpA)and aerobactin(iucA)was identified as hvKP.The patient characteristics with hvKP and cKP bacteremia were collected.The risk factors and clinical outcomes of hvKP-BSIs in Chinese patients and analysis of antibiotic resistance patterns and molecular characteristics were performed in this study,using cKP-BSIs as reference.The serotype-specific genes for the Kl,K2,K5,K20,K54,K57 capsular serotypes and another nine virulence-associated factor genes including entB,mrkD,fimH,ureA,wabG,ybtS,kfu,allS,iutA were detected in hvKP isolates by PCR.Multilocus sequence typing(MLST)of seven housekeeping genes was also performed in hvKP including amplifying and DNA sequencing.RESULTS:Overall,a total of 143 consecutive cases of K.pneumoniae BSIs were collected and 24.5%(35/143)of K.pneumoniae isolates were hvKP.Multivariate analysis implicated diabetes mellitus(OR = 3.356)and community-acquired BSIs(OR = 4.898)as independent risk factors for hvKP-BSIs,while immunosuppression(OR = 0.164)was an independent protective factor for hvKP-BSIs.We also found that patients with hvKP-BSIs had a higher WBC count than cKP infected patients(P = 0.007)when bacteremia occurred.The 30-day mortality rate of the hvKP-BSIs group was 37.1%(13/35)compared with 40.7%(44/108)in the cKP-BSIs control group(P = 0.706).The KPC-producing isolates(OR = 2.851),underlying disease with gastrointestinal fistula(OR = 3.054),APACHE II score;15(OR = 6.694)and Pitt bacteremia score,2(OR = 6.232)at infection onset were independent predictors for 30-daymortality of K.pneumoniae bacteremia patients.Both cKP and hvKP strains exhibited high antimicrobial-resistant rates for almost all tested antimicrobials.There was no statistically significant difference in the number of KPC-producing isolates between hvKP and cKP(20/35,57.1%vs 64/108,59.3%,P = 0.825).A total of 18(18/35,51.4%)isolates were positive for K1,K2,K20 and K57 serotypes,while K5 and K54 serotypes were not detected in hvKP isolates.MLST analysis revealed that the most prevalent ST in hvKP isolates was ST11(17/35,48.6%).CONCLUSION:Using a retrospective single-center study of patients with K.pneumoniae bacteremia,we clearly demonstrated that hvKP strains had a significant impact on clinical characteristics,but not on 30-day mortality.Furthermore,we found a high proportion of KPC-producing isolates among hvKP cultures in a teaching hospital in China,which underscores the added importance of epidemiologic surveillance and clinical awareness of this pathogen. |
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