多重耐药鲍曼不动杆菌整合子及菌株同源性分析

Study on the integrons and the homology of multidrug resistant Acinetobacter baumannii strains

目的了解该院多重耐药鲍曼不动杆菌(MDRAB)整合子携带情况及菌株同源性,为临床合理用药及控制院内感染提供依据。方法收集多重耐药鲍曼不动杆菌101株,K-B纸片法测定其对12种抗菌药物的敏感性,琼脂稀释法测定其对多粘菌素B的MIC;PCR检测intlⅠ、intlⅡ和intlⅢ基因及可变区;基因外重复回文序列(REP)-PCR分析菌株同源性。结果 101株MDRAB仅对米诺环素和阿米卡星呈现出敏感性,敏感率分别为36.6%和33.7%,对其他10种药物的敏感率均为0;对多粘菌素B的MIC≤2μg/mL;96.0%(97/101)菌株携带Ⅰ类整合酶基因,DNA测序分析整合子可变区携带基因盒为aacA4-catB-aadA1(2 300bp)菌株47株,携带基因盒为aacC1-orfX-orfX-orfX′-aadA1(3 000bp)菌株44株;REP-PCR分析显示耐药菌株分为A～F型,A型中又分为A1～A4,分别为21、24、11和2株;B型分为B1～B2,分别为21和12株,C型和D型各2株,F型5株,E型1株。结论本院MDRAB主要携带Ⅰ类整合子,阳性菌株大多可扩增出可变区耐药基因盒;本院存在以A型和B型克隆株为主的感染流行,必须加强院内感染防控,切断克隆菌株的传播。

Objective To study the integrons and the homology in multidrug-resistant Acinetobacter baumannii for rational use of antibiotics and control of nosocomial infections.Methods Multidrug-resistant Acinetobacter baumannii（MDRAB,n=101） were collected from clinical specimens.Antibiotic susceptibility was carried out by K-B agar diffusion and agar dilution methods.Specific PCR and DNA sequence analysis were performed for intlⅠ,intlⅡ,intl Ⅲ and variable region.The genotyping was investigated by repetitive extragenic palindromic（REP）-PCR.Results The sensitive rates of 101 MDRAB isolates to minocycline and amikacin were 36.6% and 33.7%,the MIC to polymyxin B were all lower than 2 μg/mL.Ninety seven strains were positive for intlⅠ,with 47 strains contained aacA4-catB-aadA1 box gene and 44 strains contained aacC1-orfX-orfX-orfX′-aadA1.Molecular typing revealed multiple clones,with major clonal types being nosocomially acquired and more than 90% of isolates being related to type A1～A4 and B1～B2.Conclusion IntlⅠwith the box of drug resistance gene is a major determinative factor for the resistance in MDRAB.Identifying the MDRAB phenotype with most type A and type B indicates that we should devise strategies to limit the clinical impact of these serious infections.