Hypervirulent Klebsiella pneumoniae induced ventilator-associated pneumonia in mechanically ventilated patients in China

The purpose of this study was to investigate the clinical characteristics of hypervirulent K. pneumoniae ( hvKP) induced ventilator-associated pneumonia ( VAP) and the microbiological characteristics and epidemiology of the hvKP strains. A retrospective study of 49 mechanically ventilated patients with K. pneumoniae induced VAP was conducted at a university hospital in China from January 2014 to December 2014. Clinical characteristics and K. pneumoniae antimicrobial susceptibility and biofilm formation were analyzed. Genes of capsular serotypes K1, K2, K5, K20, K54 and K57 and virulence factors plasmid rmpA( p-rmpA), iroB, iucA, mrkD, entB, iutA, ybtS, kfu and allS were also evaluated. Multilocus sequence typing ( MLST) and random amplified polymorphic DNA ( RAPD) analyses were used to study the clonal relationship of the K. pneumoniae strains. Strains possessed p-rmpA and iroB and iucA were defined as hvKP. Of 49 patients, 14 patients (28.6 %) were infected by hvKP. Antimicrobial resistant rate was significantly higher in cKP than that in hvKP. One ST29 K54 extended-spectrum-beta-lactamase (ESBL) producing hvKP strain was detected. The prevalence of K1 and K2 in hvKP was 42.9 % and 21.4 %, respectively. The incidences of K1, K2, K20, p-rmpA, iroB, iucA, iutA, Kfu and alls were significantly higher in hvKP than those in cKP. ST23 was dominant among hvKP strains, and all the ST23 strains had identical RAPD pattern. hvKP has become a common pathogen of VAP in mechanically ventilated patients in China. Clinicians should increase awareness of hvKP induced VAP and enhance epidemiologic surveillance.