Exploring the association between capsular types, sequence types, and carbapenemase genes in Acinetobacter baumannii

Acinetobacter baumannii is the main cause of nosocomial infections, which are increasingly difficult to treat due to the emergence of carbapenem resistance. This study focused on major carbapenemase genes and explored the association between carbapenemase genes, sequence types (ST types), and capsular types (K types). A total of 98 carbapenem-resistant A. baumannii (CRAB) strains were collected from two hospitals, the Chang Gung Memorial Hospital-Lin Kou branch (LCGMH) in northern Taiwan and the CGMH-Kaohsiung branch (KCGMH) in southern Taiwan, from 2015 to 2017. Major carbapenemase genes of class A, B, and D β-lactamases were detected by polymerase chain reaction. All strains except 1 were positive for bla_OXA-51-like, 76 strains (77.6%) carried bla_OXA-23-like, and 25 strains (25.5%) carried bla_OXA-24-like. The regional distribution showed that bla_OXA-23-like was more common than bla_OXA-24-like in both hospitals (85.3% and 60% in LCGMH and KCGMH, respectively); however, the percentage of bla_OXA-24-like was much higher in KCGMH (46.7%) than in LCGMH (16.2%). Oxford multilocus sequence typing and global optimal eBURST analysis were conducted for 59 strains. The results of this study showed the association between bla_OXA gene patterns, ST types, and K types and demonstrated that four major K types, KL2, KL10, KL22, and KL52, which were associated with specific ST types, were mainly clustered into clonal complexes CC208 and CC549 (a unique clonal complex found in Taiwan). These findings provide important information for monitoring the epidemiology and dissemination of this pathogen.