AdeABC外排泵系统与鲍曼不动杆菌对碳青霉烯类药物耐药的关系

AdeABC efflux pump and resistance of Acinetobacter baumannii against carbapenem

目的:探讨外排泵AdeABC系统与鲍曼不动杆菌对碳青霉烯类药物耐药的关系。方法:采用美罗培南多步法体外诱导敏感鲍曼不动杆菌获得对碳青霉烯类药物耐药的菌株;采用E-test法定量检测诱导前后菌株的敏感性;羰基氰化物间氯苯腙(carbonylcyanide-m-chlorophenylhydrazone,CCCP)抑制试验筛查外排泵;PCR及测序分析诱导前后AdeABC系统的调控基因adeS,adeR及主要碳青霉烯酶基因的变化;荧光定量PCR检测诱导前后adeA,adeB,adeR和adeS基因m RNA的表达量。结果:亲代敏感菌株S25595和S7257的美罗培南最低抑菌浓度(minimal inhibitory concentration,MIC)分别为0.38和0.25μg/m L,诱导后MIC均>32μg/m L;与亲代敏感株相比,诱导耐药株adeA,adeB,adeR和adeS基因的m RNA表达量上升2.45~9.44倍,但调控基因adeS和adeR没有基因突变或插入序列。结论:外排泵AdeABC系统高表达与鲍曼不动杆菌对美罗培南耐药密切相关,其表达水平升高不是由调控基因adeS和adeR序列中基因突变或插入序列引起,可能存在其他机制。

Objective： To investigate relationship between Acinetobacter baumannii against carbapenem. AdeABC effiux pump and resistance of Methods： Carbapenem-resistant strains were acquired from multistep selection resistance test by meropenem in vitro. The quantitation test for sensitivities of strains before and after induction was determined by the E-test, and carbonylcyanide-m-chlorophenylhydrazone （CCCP） inhibition test was used to screen efflux pump. PCR, sequencing analysis, or real-time PCR was used to analyze the changes of regulatory genes adeR and adeS of the AdeABC efflux pump system, or expressions ofadeA, adeB, adeR, and adeS in the strains before and after induction, respectivel）n Results： The minimal inhibitory concentrations （MICs） of meropenem were at 0.38 μg/mL and 0.25 μg/mL in parental sensitive strain S25595 and S7257, respectively, and the MICs of meropenem for both S25595 and S7257 after induction were more than 32 μg/mL. Compared with parental sensitive strains, the expression level of adeA, adeB, adeR, and adeS mRNA were elevated from 2.45 to 9.44 times, but there were no gene mutations or insertion sequences in the regulatory gene adeS and adeR. Conclusion： High expression of the AdeABC efflux pump system in Acinetobacter baumannii is closely associated with meropenem resistance. The upregulation ofadeA and adeB expression is not due to gene mutations in the regulatory gene adeS and adeR and other mechanisms might account for it.