大肠埃希菌对阿莫西林/克拉维酸耐药机制的研究

Mechanisms of resistance to amoxicillin/clavulanate in Escherichia coli isolates

目的探讨大肠埃希菌对阿莫西林/克拉维酸的耐药特点和机制,为临床合理用药提供依据。方法收集四川大学华西医院2005年5月至12月临床分离的544株大肠埃希菌经微量肉汤稀释法确认对氨苄西林/舒巴坦耐药的大肠埃希菌,从中随机选取276株用药敏纸片检测,仅52株对阿莫西林/克拉维酸耐药。对符合耐酶抑制剂β-内酰胺酶耐药表型的2株大肠埃希菌进行TEM型β-内酰胺酶基因的克隆表达。采用多重PCR技术检测耐阿莫西林/克拉维酸大肠埃希菌的TEM、SHV、OXA型3种β-内酰胺酶。结果52株大肠埃希菌含TEM型46株,SHV型1株,OXA型6株。其中同时含TEM型和SHV型1株以及含TEM型和OXA型5株。结论TEM-1型广谱酶的高产是华西医院大肠埃希菌对阿莫西林/克拉维酸耐药主要机制,另外本次研究首次在西南地区发现OXA-1型ESBLs,也是造成耐药的重要机制。

Objective To study amoxicillin/clavulanate-resistant Escherichia coli isolated from West China Hospital of Sichuan University, and analyze the resistant mechanisms of these isolates, so as to provide evidence for clinical therapy in infections caused by amoxicillin/clavulanate-resistant Escherichia coli. Methods Among 276 isolates showing resistant to ampicillin/sulbactam, 52 tested strains were resistant to amoxicillin/clavulanate by disk diffusion method （ inhibition zone diameter ≤ 13mm）. The genes of TEM-type enzymes in isolates of which phenotype was consistant with inhibitor-resistant TEM β-1actamase （IRT） was cloned and expressed and blaTEM, blaSHV, blaOXA genes were detected by multiple PCR. Results Multiplex PCR detected bZUTEM and blaoxA genes in 46 and 6 strains, respectively, and only one isolate had blaSHV gene. The occurrent presence of blaTEM and blaOXA genes were detected in 5 strains, and only one strain harboured blaTEM and blaSHV genes concomitantly. Conclusion In West China Hospital, overproduction of TEM-1 β-lactamases were the main mechanism in amoxicillin/clavulanate-resistant Escherichia coli isolates, while SHV-1 and OXA-1 β-lactamases were important mechanisms of resistance.