多重耐药不动杆菌16S rRNA甲基化酶和同源性研究

摘要

目的 调查2007年7月-2008年5月山西医科大学第二附属医院临床分离的61株多重耐药不动杆菌中介导氨基糖苷类抗生素高水平耐药的16S rRNA甲基化酶基因和Ⅰ类整合子携带耐药基因的分布.方法 利用blaOXA-51基因及16S rRNA-23S rRNA序列进行菌株鉴定,琼脂稀释法测定12种抗菌药物对61株不动杆菌的MIC,PCR筛选6种16S rRNA甲基化酶基因以及整合子基因盒,脉冲场凝胶电泳(PFGE)分析菌株同源性.结果 61株临床分离不动杆菌中55株为鲍曼不动杆菌、3株为3TU不动杆菌、l株13TU不动杆菌、1株醋酸钙不动杆菌、l株溶血不动杆菌.48株不动杆菌对阿米卡星、庆大霉素、妥布霉素均耐药,其中有47株检出armA基因;未检出rmtA、rmtB、rmtC、mad和npmA基因.armA基因阳性的菌株中Ⅰ类整合子阳性27株,分别携带arr-3、accA4、aacCl、catB8、aadA1和dfrA12基因.PFGE条带分析发现47株armA阳性菌株分为5个克隆,其中A、B为主要克隆,分布在我院多个科室中.结论 16S rRNA甲基化酶基因armA在多重耐药不动杆菌中广泛存在,armA基因不位于Ⅰ类整合子中,不动杆菌Ⅰ类整合子携带耐药基因主要介导对氨基糖苷类及氯霉素的耐药性.PFGE结果显示armA基因阳性菌株在我院呈克隆播散,必须采取有效的措施来控制耐药菌的传播.%Objective To characterize 16S rRNA methylase encoding genes associated with aminoglycoaides resistance, gene cassettes of class Ⅰ integrons of the multidrug-resistant Acinetobctcter spp. The sixty one Acinetobacter isolates were collected at the Second Hospital of Shanxi Medical Uni versity from July, 2007 to May, 2008. Methods Species identification was confirmed by sequence analysis of the blaOXA-51-like gene and 16S-23S rRNA gene space-region. Antimierobial susceptibility tests were performed by agar dilution method. 16S rRNA methylaae encoding genes and gene cassettes associated with integrons were amplified by PCR method. Results Among the sixty one strains, there were fifty five of Acinetobacter baumannii, three genospecies 3TU, one 13TU, one Aeinetobaeter ealcoacetieus, and one Aeinetobaeter haemolytieus. Forty eight isolates showed high-level resistance to three aminoglyeosides, including amikaein, tobramyein and gentamicin. The armA gene was found in 47 isolates and all isolates were negative for rmtA, rmtB, rmtC and rmtD genes. The Intl gene was found in 27 isolates. The gene cassettes contained arr-3, accA4,ctacCI ,catB8, aadA1 or dfrA12 genes. According to the PFGE DNA patterns, 5 distinct clones of armA-pasitive strains were identified. Clone A and Clone B were the dominant clones, widely distributed among different divisions. Condnsions 16S rRNA methylase encoding gene (armA) distributed widely in muhidrug-resistant Acinetobacter spp. The armA gene is not located in class Ⅰintegron. The class Ⅰ integron carries multiple resistant genes associated with aminoglycosides and chloramphenieol resistance.PFGE analysis suggests that armA-pesitive strains are widely spread in our hospitaL Effective infection control measure should be conducted in order to control the outbreak of resistant bacteria.