title: Molecular characterisation of multiple drug-resistant Acinetobacter baumannii isolates in southern Taiwan.
abstract: The purpose of this study was to develop a multiplex polymerase chain reaction (mt-PCR) assay for synchronous detection of carbapenem resistance genes and/or pandrug resistance genes in clinical isolates of multidrug-resistant Acinetobacter baumannii (MDR-AB) and to investigate the association between the genetic make-up and a drug-resistant pattern. In total, 213 MDR-AB isolates were collected. All clinical isolates underwent antimicrobial susceptibility testing and were analysed for the presence of oxacillinase genes (bla(OXA-23), bla(OXA-24), bla(OXA-51)-like and bla(OXA-58)), class A and C β-lactamase genes (bla(TEM-1) and bla(AmpC), respectively), and an integron-associated antibiotic resistance gene (int1) by an in-house-designed mt-PCR assay. Of the 213 isolates, 73.87% harboured both bla(TEM-1) and bla(AmpC) and 83.92% carried at least three oxacillinase genes. Moreover, 64.82% of the isolates were significant in that they had two β-lactamase genes and three oxacillinase genes (P<0.001), indicating the complexity of the genetic make-up of carbapenem-resistant A. baumannii. The bla(OXA-51)-like allele was detected in the majority of these A. baumannii isolates (97.49%), whereas bla(OXA-23) was rarely prevalent in these isolates. In multivariate logistic regression, the presence of bla(OXA-23) and bla(TEM-1) had a statistically significant association with imipenem resistance [bla(OXA-23), P=0.004, odds ratio (OR)=10.52, 95% confidence interval (CI) 2.12-52.17; bla(TEM-1), P=0.005, OR=6.14, 95% CI 1.74-21.62]. These results suggest that detecting bla(OXA-23) and bla(TEM-1) genes could be used to predict imipenem resistance in MDR-AB isolates. A mt-PCR for detecting carbapenem resistance genes and pandrug resistance genes of A. baumannii isolates was developed to provide an assay to quickly screen for potential imipenem-resistant A. baumannii in the clinic.
authors.affiliation: Department of Infectious Disease, Kaohsiung Armed Forces General Hospital, Kaohsiung, Taiwan, ROC.
authors.forename: Ren-Jy
authors.initials: RJ
authors.lastname: Ben
authors.forename: Ming-Chang
authors.initials: MC
authors.lastname: Yang
authors.forename: Jui-Chen
authors.initials: JC
authors.lastname: Hsueh
authors.forename: Jeng-Chuan
authors.initials: JC
authors.lastname: Shiang
authors.forename: Shang-Tao
authors.initials: ST
authors.lastname: Chien
mesh_terms: D000151:Acinetobacter Infections / Q000453:epidemiology* / Q000382:microbiology; D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000302:isolation & purification; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015780:Carbapenems / Q000494:pharmacology; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D006801:Humans; D015378:Imipenem / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D060885:Multiplex Polymerase Chain Reaction / Q000379:methods*; D013624:Taiwan / Q000453:epidemiology; D001618:beta-Lactamases / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems; D015378:Imipenem; D001618:beta-Lactamases; C108449:oxacillinase