Allocation of Klebsiella pneumoniae Bloodstream Isolates into Four Distinct Groups byompK36Typing in a Taiwanese University Hospital

The OmpK36 porin plays a role in carbapenem resistance and may contribute to bacterial virulence inKlebsiella pneumoniae. This study aimed to investigate the characteristics of different groups ofK. pneumoniaeseparated byompK36typing. Among 226 nonduplicateK. pneumoniaebloodstream isolates collected at a Taiwanese hospital in 2011, fourompK36types, designated types A, B, C, and D, were identified by PCR in 61, 28, 100, and 36 isolates, respectively; 1 isolate was untypeable. Statistical analysis showed significantly higher rates of antimicrobial resistance (all tested antibiotics except meropenem), extended-spectrum β-lactamases or DHA-1 (47.5% together), Qnr-type quinolone resistance determinants (50.8%), and IncFIIA-type plasmids (49.2%) in group A than in others. Seventeen isolates were identified as belonging to 3 international high-risk clones (4 sequence type 11 [ST11], 10 ST15, and 3 ST147 isolates); all isolates but 1 ST15 isolate were classified in group A. The significant characteristics of group C were hypermucoviscosity (62.0%) and a higher virulence gene content. This group included all serotype K1 (n= 30), K2 (n= 25), and K5 (n= 3) isolates, 6 of 7 K57 isolates, all isolates of major clones associated with pyogenic liver abscesses (29 ST23, 11 ST65, 5 ST86, 7 ST373, and 1 ST375 isolates), and 16 (94.1%) of 17 isolates causing bacteremic liver abscesses. Twelve (42.9%) of the group B isolates were responsible for bacteremic biliary tract infections. Group D was predominant (83.3%) among 12 K20 isolates. This study suggests that most clinicalK. pneumoniaeisolates can be allocated into four groups with distinct characteristics based onompK36types.