국내 Acinetobacter 임상분리주의 adeG, adeB, adeE, adeY, abeM 및 adeJ 유출펌프 유전자의 분포

Abstract

Background: Acinetobacter such as Acinetobacter baumannii has become a common opportunistic pathogen in hospital. Drug efflux is one of the major mechanisms of antimicrobial resistance in A. baumannii. Increased expression of chromosomal genes for efflux systems plays a major role in multidrug resistance (MDR). The aim of present study was to determine the frequency of six efflux pump genes in Acinetobacter clinical isolates collected from South Korean hospitals. Materials and methods: The total of 339 Acinetobacter strains used in this study consisted of 279 Acinetobacter baumannii-calcoaceticus complex (ABC) and 60 non-ABC Acinetobacter strains. The ABC consisted of 154 A. baumannii, 94 Acinetobacter nosocomialis, 7 Acinetobacter calcoaceticus, and 24 Acinetobacter pittii. The 154 strains of A. baumannii consisted of 68 strains obtained from the various regions of Korea in 2012 and 86 strains obtained at Chosun University Hospital for 5 years. We identified ABC to the species level using gyrB multiplex PCR 1 and 2 method and Acinetobacter species-specific PCR method. A. baumannii was identified using gyrB multiplex 1 PCR and blaOXA51-likePCR. The 60 non-ABC Acinetobacter strains were identified using rpoB sequencing analysis. We performed specific PCR assays to detect adeG, adeB, adeE, adeY, abeM, and adeJ which are respective transporter genes of the multidrug efflux pump AdeFGH, AdeABC, AdeDE, AdeXYZ, AbeM and AdeIJK. The distribution of adeG, adeB, adeE, adeY, abeM, and adeJ was investigated according to the Acinetobacter species, MDR status, susceptibility to imipenem or ciprofloxacin, and collection time and region of Acinetobacter strains. Results: Frequency of six efflux pump genes of adeG, adeB, adeE, adeY, abeM, and adeJ showed significant difference among 14 groups of Acinetobacter species. The frequency of efflux pump gene in A. baumannii group and A. nosocomialis group were 13.6% and 72.3% (p<0.0001) for adeE, 95.5% and 24.5% (p<0.0001) for abeM, and 98.1% and 79.8% (p<0.0001) for adeJ, respectively. The frequency of adeB, adeE, adeY, and adeJ showed significant difference among the SAB, MDRAB, and XDRAB groups of 154 strains of A. baumannii. Comparison pairs showing statistically significant differences (P<0.05) by Chi-square test were as follows: SAB vs. MDRAB (73.8 vs. 96.7%, respectively; p=0.003) and SAB vs. XDRAB (73.8 vs. 92.2%, respectively; p=0.040) in adeB; MDRAB vs. XDRAB (1.6 vs. 25.5%, respectively; p=0.001) in adeE; SAB vs. MDRAB (21.4 vs. 1.6%, respectively; p<0.0001) and SAB vs. XDRAB (21.4 vs. 2.0%, respectively; p<0.001) in adeY; SAB vs. MDRAB (92.9 vs. 100%, respectively; p=0.029) and SAB vs. XDRAB (92.9 vs. 100%, respectively; p=0.038) in adeJ. The frequency of efflux pump gene in imipenem-susceptible and imipenem-nonsusceptible group was significantly different for adeE (77.1 vs. 94.3%%, respectively; p=0.002), for adeY (18.8 vs. 1.9%, respectively; p<0.0001), and for adeJ (93.8 vs. 100%, respectively; p=0.010). The frequency of efflux pump gene in ciprofloxacin-susceptible and ciprofloxacin-nonsusceptible group were significantly different for adeB (75.6 vs. 93.8%, respectively; p=0.003), and for adeY (22.0 vs. 1.8%, respectively; p<0.0001). No significant difference was found in the frequency of all efflux pump genes among groups of collection regions of Korea of 86 strains of A. baumannii collected in 2012. The frequency of 6 efflux pump genes of 86 strains of A. baumannii collected from Chosun University Hospital was compared according to the group of the year, season, and month of collection, respectively. The frequency of adeG and adeE showed significant difference among 5 groups of collection year. The frequency of adeY showed significant difference among 4 groups of collection season of those strains. The frequency of adeG, adeE, adeY, and abeM efflux pump genes showed significant difference among 12 groups of collection month of those strains. Conclusion: The frequency of six efflux pump genes of adeG, adeB, adeE, adeY, abeM and adeJ showed significant difference among 14 group of Acinetobacter species of 339 strains of Acinetobacter clinical isolates from Korean hospitals. It seems to be that adeB and adeJ may be related to the antimicrobial resistance of A. baumannii. These findings would be beneficial for epidemiologic study of MDR Acinetobacter species related to efflux pump resistance mechanism in Korea.