多重耐药性鲍曼不动杆菌耐药基因及菌株聚类分析

Drug-resistant genes and cluster analysis in multidrug-resistant Acinetobacter baumannii

目的了解临床分离到的鲍曼不动杆菌耐药相关基因存在状况和菌株间的亲缘性。方法药敏试验用PhoenixTM100系统检测。用PCR扩增β-内酰胺酶基因、氨基糖甙类药物修饰酶基因、DNA拓扑异构酶基因等,并用DNA测序仪证实。结果247株鲍曼不动杆菌对亚胺培南和美洛培南耐药率最低,仅为3.2%、4.1%。20株多重耐药性鲍曼不动杆菌中,17株具TEM型β-内酰胺酶基因,氨基糖甙类药物修饰酶基因aac（3）-Ⅰ、aac（3）-Ⅱ、aac（3）-Ⅲ、aac（3）-Ⅳ、aac（6′）-Ⅰ、ant（2″）-Ⅰ、ant（3″）-Ⅰ基因检出率分别为80%、15%、30%、70%、15%、55%、80%。20株对环丙沙星耐药的鲍曼不动杆菌gyrA密码子均由TCA→TTA,氨基酸由Ser83→Leu,而85%菌株（17/20）的ParC氨基酸序列发生Ser80→Leu替代。聚类分析显示存在2株克隆株,其耐药表型基本一致。结论本院鲍曼不动杆菌携带多种β-内酰胺酶、氨基糖甙类修饰酶等耐药基因,喹诺酮耐药决定区基因突变是细菌耐受喹诺酮类药物重要原因。聚类分析表明,本院的鲍曼不动杆菌存在克隆传播。

Objective To investigate drug-resistant genes and phylogenetic relationship in Acinetobacter baumannii isolated from clinical specimens. Methods Antimicrobial susceptibility tests were performed by Phoenix^TM-100 system. Resistant genes encoding β-lactamases, aminoglycoside-modiying enzymes（AMEs） and DNA topoisomerases were amplified by PCR and confirmed by DNA sequencer. Results The rate of 247 isolates in Acinetobacter baumannii resistant to imipenem and meropenem was only 3.2% and 4.1%, respectively. Seventeen strains in 20 Acinetobacter baumannii carried TEM type β-lactamase genes. The AME positive rate of aac（3）- Ⅰ , aac（3）-Ⅱ , aac（3）-Ⅲ, aac （3）-Ⅳ, aac（6＇）-Ⅰ , ant（2＂）- Ⅰ and ant（3＂）-1 was 80%, 15%, 30%, 70%, 15%, 55% and 80%, respectively. All 20 strains of Acinetobacter baumannii showed a change at Ser83 to Leu in gyrA protein. In addition, 17 strains of 20 Acinetobacter baumannii in parC protein presented a change at Ser80 to Leu. Cluster analysis indicated that there were two clones in 20 strains and its resistant phenotype was similar. Conclusion Acinetobacter baumannii has carried many resistant genes encoding β-lactamases and aminoglycoside modifying enzymes in our hospital. It is also demonstrated that the mutation of quinolone resistant determining region attributes to bacterial resistant to quinolones. In addition, cluster analysis indicates that the spread of clonies occurred in our hospital.