耐碳青霉烯类鲍曼不动杆菌分子流行病学及耐药机制研究

Research on molecular epidemiology and resistance mechanism of carbapenems resistant Acinetobacter baumannii

目的探讨院内鲍曼不动杆菌的基因同源性及其介导对碳青霉烯类药物耐药的可能机制。方法采用琼脂稀释法检测临床分离81株鲍曼不动杆菌对常用的12种抗菌药物的最低抑菌浓度。采用脉冲场凝胶电泳(PFGE)技术对临床分离株进行基因分型;PCR技术检测临床菌株β-内酰胺类水解酶基因及3个外排系统AdeABC、AdeIJK及AdeFGH的主要结构基因的携带情况,比较其在亚胺培南耐药组和敏感组中的分布差异。结果 81株鲍曼不动杆菌对临床常用的12种抗菌药物普遍耐药,对米诺环素的耐药率最低(30.9%),对亚胺培南的耐药率为53.1%,对其他抗菌药物的耐药率均超过60%。81株鲍曼不动杆菌PFGE分型主要为A、B、C、D、E、F、G共7型,其中A型为主要流行株。所有菌株中均携带OXA-51基因,未检测到OXA-24、OXA-58、VIM-1及VIM-2基因。β-内酰胺酶基因AmpC、OXA-23与IMP-1的检出率分别为83.9%(68/81)、71.6%(51/81)和54.3%(44/81),外排泵基因adeB、adeJ与adeG的检出率分别为77.8%(63/81)、92.6%(75/81)和90.1%(73/81);统计学分析结果显示:β-内酰胺酶基因AmpC(χ2=8.9,P<0.05)与OXA-23(χ2=28.05,P<0.05)及外排泵基因adeB(χ2=9.5,P<0.05)与adeG(χ2=5.20,P<0.05)在亚胺培南耐药组和亚胺培南敏感组中的分布率比较,差异均具有统计学意义。结论鲍曼不动杆菌临床分离株耐药严重且存在院内流行,主要为A型流行株。β-内酰胺酶基因Amp-C、OXA-23的产生及主动外排系统AdeABC及AdeFGH在介导鲍曼不动杆菌碳青霉烯药物耐药中发挥重要作用。

Objective To investigate the gene homology of Acinetobacter baumannii clinical isolates in hospital, and explore the main carbapenems resistance mechanism Of Acinetobacter baumannii. Methods The minimal inhibitory concentrations of 12 antimierobial agents against 81 Acinetobacter baumannii clinical isolates were determined by agar dilution method. Pulsed-field gel electrophoresis （PFGE） was employed to type 81 Acinetobacter baumannii isolates. PCR was used to detect the genes of β-1actamases and main structural genes of adeABC, adeIJK and adeFGH efflux pump system, and the distributions of these genes in imipenem resistant Acinetobacter baumannii group and imipenem sensitive Acinetobacter baumannii group were compared. Results Eighty-one Acinetobacter baumannii clinical isolates were commonly resistant to 12 antimicrobial agents, with the lowest resistance rate of 30.9% for polymyxin B, the second lowest resistance rate of 53.1% for imipenem, and resistance rates over 60% for the other antimicrohial agents. Eighty-one Acinetobacter baumannii strains were classified into 7 types based on PFGE pulsotypes, named type A, B, C, D, E, F and G. Isolates of type A were the main epidemic strains. All the strains carried OXA-51 gene, and OXA-24, OXA-58, VIM- 1 and VIM-2 genes were not detected. The detection rates of AmpC, OXA-23 and IMP-1 of β-lactamase genes were 83.9% （68/81）, 71.6% （51/81） and 54.3% （44/81） respectively, and those of adeB, adeJ, and adeG of efflux pump genes were 77.8% （63/81）, 92.6% （75/81） and 90.1% （73/81） respectively. Statistical analysis revealed that the distribution rates of AmpC （ X^2 = 8.9, P 〈 0.05）, OXA-23 （ X^2 = 28.05, P 〈 0.05）, adeB （ X^2 = 9.5, P 〈 0.05） and adeG （~2 =5.20, P 〈 0.05） in imipenem resistant Acinetobacter baumannii group were significantly different from those in imipenem sensitive Acinetobacter baumannii group. Conclusion There has been clonal spread of Acinetobacter baumannii stains among patients in hospital, which are mainly type A strain. ^-lactamases genes Amp-C and OXA-23 and efflux pump systems adeABC and adeFGH may play an important role in the carbapenems resistance mechanism of Acinetobacter baumannii.