大肠埃希菌对阿莫西林/克拉维酸耐药机制的研究

The mechanism of E.coli of resistance to amoxicillin/clavulanate

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,从而为临床合理用药及减少耐药的发生和耐药基因传播提供实验研究依据。方法将对氨苄西林/舒巴坦耐药的大肠埃希菌544株,随机选取276株进行阿莫西林/克拉维酸纸片的筛查,对筛出的耐药菌株采用琼脂对倍稀释法进行MIC值测定和PCR扩增分析。对符合耐酶抑制剂β-内酰胺酶耐药表型的大肠埃希菌进行TEM型β-内酰胺酶基因的克隆表达。采用多重PCR技术对耐阿莫西林/克拉维酸大肠埃希菌进行TEM、SHV、OXA型三种β-内酰胺酶的筛查。结果TEM型46株,SHV型1株,OXA型6株,TEM型和SHV型均阳性1株,TEM型和OXA型均阳性5株。产TEM型β-内酰胺酶中TEM-1型最常见,耐酶抑制剂TEM型β-内酰胺酶(IRT)未发现。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,本研究首次在西南地区发现OXA-1,是造成耐药的重要原因。

Objective To study the mechanism of E. coli of resistance to amoxicillin/clavulanate. Methods The susceptibility of amoxieillin/clavulanate resistant E. coli isolates revealed by disk diffusion method to antibacterial agents were assayed by agar dilution testing. The genotypes were detected by PCR analysis. The genes of TEM-type enzymes in isolates of which phenotype was consistant with inhibitor-resistant TEM β-lactamase （IRT） were cloned and expressed. The multiplex PCR was to discriminate blaTEM, blaSHV and blaOXA genes. Results blaTEM, blaOXA and blaSHV genes were detected in 46, 6 and 1 strains, respectively. There were 5 strains contained blaTEM and blaOXA genes, simultaneously. TEM-type enzymes TEM-1 was frequent genes in amoxicillin/clavulanate resistant E. coli isolates. Con-clusion In West China Hospital, hyperproduction of TEM-1 and β-lactamases are the main mechanism in Eseherichia coli resistant to amoxicillin/clavulanate.