Molecular And Virulence Characterization Of Carbapenem-resistant Klebsiella Pneumoniae Collected From A Teaching Hospital

Background and ObjectivesKlebsiella pneumonia is one of the most common germs of hospital-acquired infections. The emergence of carbapenem-resistant K. pneumonia constitutes a severe public health threat. The acquisition of carbapenemase genes is the major way to confer antibiotic resisitance. A new hypervirulent variant of K. pneumonia (hvKP) has emerged and recognized in many regions recently, however, little is known about the virulence determinants of the carbapenem-resistant K. pneumonia.The carbapenemase-encoding gene and the molecular epidemiology of carbapenem-resistant K. pneumonia (CRKP) in a university hospital were investigated. The virulence determinants of the CRKPs were also analyzed.Methods138 strains of CRKPs were isolated from clinical specimens from January 2014 to December 2014 in the First Affiliated Hospital of Zhejiang University. Bacterial identification and antimicrobial susceptibility testing were carried out with VITEK 2 Compact automatic microbiological assay system. The detection of carbapenemase-producing K. pneumoniae was confrimed by modified Hodge test. Screening of carbapenemase-encoding gene, multilocus sequence typing (MLST) and replicon typing of plasmid were conducted by PCR and sequencing. K. pneumonia strains with a positive string test were designated as hvKP. Screening of virulence genes were identified by PCR and sequencing.ResultsAll the 138 strains showed highly multi-drug resistance to the antibiotics commonly used.127 strians (92.0%) were confirmed as carbapenamase pruducers by modified Hodge test. Carbapenemase-encoding gene was identified in 125 isolates of K. pneumoniae; among which 124 contained blaKPC-2 (89.9%) and 1 was blaIMP-4.MLST revealed 24 different ST types, including 2 new STs. ST11 was the most abundant type (96 isolates,69.6%), followed by ST13 (9 isolates) and ST437 (7 isolates). PCR-based replicon typing showed that IncF was the major plasmid incompatibility groups (100 isolates,72.5%). Capsular genotypes K1 and K2 comprised 5.1%(7/138) and 21.0% (29/138) of all K. pneumoniae strains. The majority of K. pneumoniae strains possessed mrkD (94.2%), entB (73.2%), ybtS (81.2%), fimH (83.3%) and kpn (78.3%). The prevalence of alls and kfu was 2.2% and 10.1% respectively. Of all the CRKPs,26 (26/138,18.8%) were positive for string test. ST11 (17/26,65.4%) was dominant among hvKP strains, followed by ST17 and ST716. The incidences of rmpA, iutA, wcaG and coexist of entB, ybtS and iutA were significantly higher in hvKP than in cKP.ConclusionsKPC-2 carbapenemase was the major mechanism of bacterial resistance to carbapenems. The dissemination of KPC-2-producing K. pneumoniae in this study appeared to be clonal, and the ST11 K. pneumoniae was the predominant clone. The IncF group plasmids were the most common plasmids for the carbapenem-resistant K. pneumonia. ST11 was dominant among hvKP strains. The RmpA, IutA, WcaG and combination of different iron-acquisition systems may contribute to the increased virulence of hvKP. The strains simultaneously hypervirulent and multidrug resistance have emerged in this hospital, which suggests an urgent need to enhance clinical awareness, epidemiologic surveillance and infection control.