Prevalence of multi-drug resistant acinetobacter baumannii from a healthcare facility of Gangwon province in Korea

Abstract

The multidrug-resistant (MDR) Acinetobacter baumannii has emerged as a significant infectious agent in hospitals worldwide. A. baumannii was previously considered an opportunistic pathogen of relatively low virulence. However, recent reports from various locations around the world suggest that A. baumannii is now frequently isolated and is associated with severe infections and adverse outcomes. The purpose of this study was to determine the genetic basis for MDR and the clonal relationship among A. baumannii clinical isolates obtained from a university hospital in Gangwon province of Korea. To estimate the prevalence of antibiotic resistance determinants, PCR assays and sequence analysis were performed for the detection of β-lactamases, 16S rRNA methylase, aminoglycoside-modifying enzymes, and quinolone resistance determining regions (QRDR). Amplified fragment length polymorphism (AFLP) and repetitive sequence-based polymerase chain reaction (REP-PCR) were performed to determine the clonal relatedness of MDR A. baumannii. All of the MDR A. baumannii isolates were encoded by both blaOXA-23-like and blaOXA-51-like genes and all isolates with the blaOXA-23-like gene had the upstream element ISAba1 to promote increased gene expression and subsequent resistance to carbapenemase. In all A. baumanni, those isolates encoded by blaAmpC had ISAba1 inserted upstream of blaAmpC. Eighty-one A. baumannii were encoded by the blaADC-7-like gene. To investigate aminoglycoside resistance, 16S rRNA methylase gene armA was detected in 70 (81%) clinical isolates, and phosphotransferase genes encoding aac(3)-Ia and aac(6'')-Ib were the most prevalent. A combination of 16S rRNA methylase and aminoglycoside-modifying enzyme genes (armA, aac(3)-Ia, aac(6'')-Ib, and aph(3'')-Ia) were found in 45 (52%) isolates. The sequencing results for the QRDR of gyrA and parC revealed the presence of Ser (TCA) 83 Leu (TTA) and Ser (TCG) 80 Leu (TTG) substitutions in the respective enzymes for all MDR A. baumannii isolates sequenced. Moreover, all of the A. baumannii isolates showed very similar or identical band patterns on REP-PCR and AFLP profiles, suggesting that they had originated from a common ancestor and clonally spread in the university hospital in Gangwon province. The clonal spread of MDR A. baumannii is a major factor contributing to the growing problem of antimicrobial resistance. Molecular typing for MDR A. baumannii could be helpful in confirming the identification of a common source or cross-contamination. This is an important step in enabling epidemiological tracing of these strains.