The Genetic Characteristics of Multidrug-resistant Acinetobacter baumannii Coproducing 16S rRNA Methylase armA and Carbapenemase OXA-23

ABSTRACT

Acinetobacter baumannii is a gram-negative organism reported worldwide as a cause of health-care associated infections. Due to its increasing drug resistance, several studies on coproduction of armA and carbapenemase in South Korea and other parts of the world were reported, which can pose significant therapeutic threat. The aim of this study was to investigate genetic characteristics of multidrug-resistant A. baumannii coproducing armA and carbapenemase and its epidemiological relatedness. Forty-five multidrug resistant (MDR) A. baumannii clinical isolates were collected. Antimicrobial susceptibility was determined by agar dilution, Etest and VITEK 2 system. The presence of 16S rRNA methylase and carbapenemase were analyzed by polymerase chain reaction (PCR) and sequencing. Repetitive element palindromic (REP)-PCR was also performed for epidemiologic investigation. All of A. baumannii isolates harbored blaOXA-51 -like gene and 10 isolates showed an upstream ISAba1. 36 isolates (80%) showed amplification of OXA-23, all of which except one had an upstream ISAba1. 16S rRNA methylase armA was found in 44 isolates with high level resistance to aminoglycosides. The rate of coproduction was found in 36 isolates (80%). All isolates showed dominant two patterns in REP-PCR profile. The prevalence of MDR A. baumannii coproducing OXA-23 and armA was high, which the rate of blaOXA-23 coproduction was also high.