Distribution and Molecular Characterization of Acinetobacter baumannii International Clone II Lineage in Japan

Abstract

Multidrug-resistant (MDR) <i>Acinetobacter</i> spp. have been globally disseminated in association with the successful clonal lineage <i>Acinetobacter baumannii</i> international clone II (IC II). Because the prevalence of MDR <i>Acinetobacter</i> spp. in Japan remains very low, we characterized all <i>Acinetobacter</i> spp. (<i>n</i> = 866) from 76 hospitals between October 2012 and March 2013 to describe the entire molecular epidemiology of <i>Acinetobacter</i> spp. The most prevalent species was <i>A. baumannii</i> (<i>n</i> = 645; 74.5%), with <i>A. baumannii</i> IC II (<i>n</i> = 245) accounting for 28.3% of the total. Meropenem-resistant isolates accounted for 2.0% (<i>n</i> = 17) and carried IS<i>Aba1-bla</i>_OXA-23-like (<i>n</i> = 10), <i>bla</i>_IMP (<i>n</i> = 4), or IS<i>Aba1-bla</i>_OXA-51-like (<i>n</i> = 3). Multilocus sequence typing of 110 representative <i>A. baumannii</i> isolates revealed the considerable prevalence of domestic sequence types (STs). <i>A. baumannii</i> IC II isolates were divided into the domestic sequence type 469 (ST469) (<i>n</i> = 18) and the globally disseminated STs ST208 (<i>n</i> = 14) and ST219 (<i>n</i> = 4). ST469 isolates were susceptible to more antimicrobial agents, while ST208 and ST219 overproduced the intrinsic AmpC β-lactamase. <i>A. baumannii</i> IC II and some <i>A. baumannii</i> non-IC II STs (e.g., ST149 and ST246) were associated with fluoroquinolone resistance. This study revealed that carbapenem-susceptible <i>A. baumannii</i> IC II was moderately disseminated in Japan. The low prevalence of acquired carbapenemase genes and presence of domestic STs could contribute to the low prevalence of MDR <i>A. baumannii</i> A similar epidemiology might have appeared before the global dissemination of MDR epidemic lineages. In addition, fluoroquinolone resistance associated with <i>A. baumannii</i> IC II may provide insight into the significance of <i>A. baumannii</i> epidemic clones.