阴沟肠杆菌AmpC酶检测及对酶抑制剂复合制剂稳定性研究

Detection of AmpC β-Lactamases from Enterobacter cloacae and Study of Stability to Compound Agents of Enzyme Inhibitors

目的了解阴沟肠杆菌产AmpC酶的状况及对酶抑制剂复合制剂的稳定性。方法应用头孢西丁三维试验检测AmpC酶,并对AmpC阳性者行接合试验,采用KB琼脂扩散法做药敏试验,并测定AmpC阳性株对不同酶抑制剂复合制剂的相对水解率。结果在受检的80株阴沟肠杆菌中,24株产AmpC酶,4株接合成功,接合子的耐药率明显增加;对AmpC阳性株行药敏试验示,亚胺培南的敏感率为91.7%;头孢吡肟和头孢哌酮/舒巴坦分别为87.5%和75.0%;哌拉西林/他唑巴坦为54.2%;阿莫西林/克拉维酸为20.8%;对5种抗菌药物的相对水解率为阿莫西林/克拉维酸最高;其次是哌拉西林/他唑巴坦、头孢哌酮/舒巴坦和头孢吡肟;亚胺培南最稳定。结论对于产AmpC酶的阴沟肠杆菌亚胺培南具有较强的抗菌活性且较稳定,头孢吡肟和头孢哌酮/舒巴坦次之,哌拉西林/他唑巴坦较弱。

OBJECTIVE To investigate the production of AmpC β lactamases from Enterobacter cloacae and the stability to the compound agents of enzyme inhibitors. METHODS Cefoxitin three dimensional test was used to detect AmpC enzyme. Transconjugation test was given to AmpC positive strains. Sensitivity of drugs was detected by Kirby Bauer agar diffusion method. In addition, relative hydrolytic rates were measured for AmpC positive strains to different compound agents of enzyme inhibitors. RESULTS Among 80 clinical isolates of E. cloacae, 24 strains produced AmpC β lactamases. In 24 AmpC positive strains, 4 were successfully conjugated and the resistant rates of transconjugants increased obviously. Susceptible rate to imipenem, was 91.7%, and to cefepime and cefoperazone/sulbactam was 87.5% and 75.0%, respectively, and to piperacillin/tazobactam and amoxicillin/clavulanic acid was 54.2% and 20.8%, respectively by sensitivity test of drugs to AmpC positive strains. The results of relative hydrolytic rates to five antibiotics showed amoxicillin/clavulanic acid was more quickly hydrolyzed, then followed by piperacillin/tazobactam, cefoperazone/sulbactam and cefepime. Imipenem was the most stable. CONCLUSIONS Imipenem has more antibacterial activity and stability, the next are cefepime and cefoperazone/sulbactam; piperacillin/tazobactam is less active and tess stable for AmpC β lactamases producing E. cloacae.