Molecular characterization of carbapenemase genes in Acinetobacter baumannii in China

Acinetobacter baumannii is an aerobic non-motile Gram-negative coccobacillus, and it is one of the most important nosocomial pathogens worldwide. The aim of this study was to determine the molecular epidemiology of the outbreak strains. Between March 2011 and March 2014, a total of 205 strains of A. baumannii were isolated from patients at the Nanyang City Center Hospital. The blaOXA-23, blaOXA-24, blaOXA-51, and blaOXA-58 genes were amplified by multiplex polymerase chain reaction. We found that 68 (33.17%) strains were positive for the blaOXA-23 gene, and 88.24% of these 68 showed resistance to carbapenems, while 11.76% were sensitive to carbapenems. The blaOXA-51 gene was found in 132 (64.39%) strains, and 17.42% of these were resistant to carbapenems while 82.58% were sensitive to carbapenems. Moreover, 5 (2.44%) strains were positive for blaOXA-58, of which 80% were resistant to carbapenems and 20% were sensitive to carbapenems. We found that A. baumannii showed 100% drug resistance to ampicillin, cefotetan, cefazolin, and cefoperazone. Our findings suggest that the blaOXA-23 and blaOXA-51 genes are most frequently identified in A. baumannii, while blaOXA-23 is the most important gene for resistance to carbapenems.