多药耐药鲍氏不动杆菌adeABC外排系统研究

目的 调查临床多药耐药鲍氏不动杆菌外排泵耐药基因adeA、adeB、adeC和调控基因adeS、adeR分布情况及与抗菌药物耐药的关系.方法 在全国范围21所医院选择同期多药耐药鲍氏不动杆菌101株和敏感菌12株进行研究；测定其对6种抗菌药物的MIC值；PCR筛选外排泵耐药基因adeA、adeB、adeC及其调控基因adeS、adeR,克隆测序明确基因型.结果 101株多药耐药鲍氏不动杆菌对美罗培南、亚胺培南、米诺环素、头孢噻肟、庆大霉素、环丙沙星耐药率分别为52.5％、62.4％、71.3％、80.2％、94.1％、95.0％,其中对以上6种抗菌药物全部耐药的菌株36株；adeA、adeB、adeC、adeS、adeR基因阳性菌株分别为74、76、75、73、77株；以上5种基因均阳性(基因型命名为组Ⅰ)的菌株检出64株,检出率为63.4％,为分布最广且最主要的基因型；根据脉冲场凝胶电泳菌株的同源性分析结果发现,克隆A、B、C、E中以组Ⅰ为主,而D克隆中以组Ⅶ(5种基因均阴性)为主；12株敏感鲍氏不动杆菌外排泵耐药基因adeA、adeB、adeC阳性率也均＞40.0％,但调控基因adeS、adeR阳性率较低.结论 鲍氏不动杆菌临床分离株中,adeABC外排泵基因在耐药菌和敏感菌中阳性率均高,而且地区分布和克隆分布十分广泛,其与多耐药的获得有极大的相关性,其基因的播散可能主要通过菌株的克隆播散得以实现.

Study on AdeABC efflux pump mechanism in multidrug-resistant Acinetobacter baumannii

OBJECTIVE To investigate the distribution of efflux system AdeABC coding genes(adeA,adeB,adeC) and regulating genes(adeR,adeS) in multi-drug resistant Acinetobacter baumannii(MDRAB),and analyze the relationship between the efflux system and the antibiotic resistance of MDR-AB. METHODS A total of one hundred and one isolates of MDR-AB and twelve isolates of antibiotic susceptible A.baumannii were collected from 21 hospitals in China.The MIC values of 6 antimicrobial agents against these strains were determined by Agar dilution.The gene sequences of adeABC efflux system were amplified and PCR products were purified and sequenced. RESULTS The resistance rate of 101 isolates of MDR-AB to memropenem,imipenem,minocycline,cefotaxime,gentamycin,and ciprofloxacin was 52.5%,62.4%,71.3%,80.2%,94.1% and 95.0%,respectively.Among them,36 isolates(35.6%) were resistant to all these six drugs.PCR and sequence analysis revealed that 74,76,75,73 and 77 isolates were positive for adeA,adeB,adeC,adeS and adeR genes in the 101 MDR-AB isolates.Furthermore,64 isolates(63.4%) were positive for all the five genes(genotype named group Ⅰ),which was the most widely distributed and the predominant genotype.According to PFGE analysis,most isolates of clones A,B,C and E belonged to group Ⅰ,while the most isolates of clone D were negative for all the five genes(group Ⅶ).In 12 susceptible isolates,the positive rates of coding genes adeA、adeB and adeC were all above 40%,while the positive rates of regulating genes adeS and adeR were 25% and 16.7%,respectively. CONCLUSION There are high positive rates of AdeABC efflux system genes in both multi-drug resistant and susceptible clinical isolates of A.baumannii.They are widely distributed among regions and clones.The efflux system may have close correlation with multi-drug resistance of A.baumannii.Gene spread may be mainly realized through clonal spread.