Molecular Epidemiology of Emerging Carbapenem Resistance inAcinetobacter nosocomialisandAcinetobacter pittiiin Taiwan, 2010 to 2014

Abstract

ABSTRACTThis study investigated the molecular epidemiology of carbapenem-resistantAcinetobacter nosocomialisandAcinetobacter pittii(ANAP). Clinical isolates ofAcinetobacterspp. collected by the biennial nationwide Taiwan Surveillance of Antimicrobial Resistance program from 2010 to 2014 were subjected to species identification, antimicrobial susceptibility testing, and PCR for detection of carbapenemase genes. Whole-genome sequencing or PCR mapping was performed to study the genetic surroundings of the carbapenemase genes. Among 1,041Acinetobacterisolates, the proportion of ANAP increased from 11% in 2010 to 22% in 2014. The rate of carbapenem resistance in these isolates increased from 7.5% (3/40) to 22% (14/64), with a concomitant increase in their resistance to other antibiotics. TheblaOXA-72andblaOXA-58genes were highly prevalent in carbapenem-resistant ANAP. Various genetic structures were found upstream ofblaOXA-58in different plasmids. Among the plasmids found to containblaOXA-72flanked by XerC/XerD, pAB-NCGM253-like was identified in 8 of 10 isolates. Conjugations of plasmids carryingblaOXA-72orblaOXA-58toA. baumanniiwere successful. In addition, three isolates with chromosome-locatedblaOXA-23embedded in AbGRI1-type structure with disruption of genes other thancomMwere detected. Two highly similar plasmids carrying class I integron containingblaIMP-1and aminoglycoside resistance genes were also found. The universal presence ofblaOXA-272/213-likeonA. pittiichromosomes and their lack of contribution to carbapenem resistance indicate its potential to be a marker for species identification. The increase of ANAP, along with their diverse mechanisms of carbapenem resistance, may herald their further spread and warrants close monitoring.