大肠埃希菌中检出多种质粒介导的AmpC酶

Identification of plasmid-mediated AmpC β-lactamase in Escherichia coli

目的了解安徽省产质粒介导的 AmpC β内酰胺酶细菌的基因型特征及耐药性。方法收集临床分离无重复大肠埃希菌共407株,采用头孢西丁三维试验检测 AmpC 酶,琼脂稀释法检测耐药性,PCR 扩增各组基因及测序以确定 AmpC 酶基因型。结果头孢西丁三维试验阳性率为8.1%(33/407),其中质粒介导的 AmpC β内酰胺酶的检出率为3.0%(12/407)。PCR 扩增和测序结果证实为5株 bla_(CMY-2)、4株 bla_(DHA-1)和2株 bla_(ACT-2)基因,并发现1株新的 CMY 型基因,DNA 测序表明该基因和 CMY-2有97%的同源性,并在国内首次发现 bla_(ACT-2)基因。药敏试验显示对头霉素和哌拉西林耐药,对亚胺培南100%敏感,2株产 DHA-1型酶的菌株对头孢吡肟耐药。结论安徽省各地区已有质粒介导 AmpC 酶的出现,基因型有 CMY-2、DHA-1和 ACT-2。碳青霉烯类药物可作为治疗产质粒介导的 AmpC 酶细菌感染的首选药物。

Objective To investigate genotypes and antibiotic resistance of Escherichia coli producing plasmid-mediated AmpC β-lactamase in Anhui province. Methods A total of 407 clinical isolates of nonrepeated Escherichia coli were collected from different cities in Anhui province. AmpC β-lactamase producing isolates were identified by cefoxitin three-dimensional test and antibiotic susceptibility was identified by agar dilution test. Plasmid extraction, PCR amplication of corresponding group was performed, followed by sequencing. Results The positive rate of cefoxitin three-dimensional test was 8. 1% （33/407）, and the prevalence of plasmid-mediated AmpC β-lactamase was 3.0 % （ 12/407 ）. blaCMY-2 gene, blaDHA-1 gene and blaACT-2 gene were identified by PCR amplification and confirmed by sequencing in 5 strains, 4 strains and 2 strains, respectively. A new CMY genotype was identified, with its sequence revealed 97% identity to the deduced amino acid sequence with previous CMY-2. This is also the first report on ACT-2 genotype in China. The susceptibility test showed that all strains were resistant to cephamycins and piporacillin, and susceptible to imipenem Two strains of Escherichia coli producing DHA-1 were resistant to fourth-generation cephalosporin. Conclusions CMY-2, DHA-1 and ACT-2 axe the most common genotypes in plasmid-mediated AmpC β-lactamase produced by clinical Escherichia coli isolates in Anhui province. Carbaponems could be the first choice for the treatment of infection caused by AmpC β-lactamase producers.