海南地区产质粒介导AmpC酶大肠埃希菌基因型研究

Genotype of β-lactamases in plasmid-mediated AmpC of Escherichia coli in Hainan

目的了解海南地区产质粒介导AmpC酶大肠埃希菌基因型特点。方法收集来自海南地区8所医院2009年度不重复临床分离的大肠埃希菌540株,分别采用纸片扩散法和三维试验进行表型筛选和AmpC酶检测,用接合试验证实酶基因型的转移性,通过PCR检测及序列分析进行质粒AmpC酶基因型确定,用E-Test法对产质粒AmpC酶株进行MIC测定。结果 540株大肠埃希菌中,头孢西丁抑菌环直径≤17 mm的占22.8%(123/540),除五指山市菌株全部对头孢西丁敏感外,其他医院均有对头孢西丁的耐药株。酶提取物三维试验检测阳性的占1.9%(10/540),以PCR方法对10株三维试验阳性大肠埃希菌进行基因检测,结果6株在约462 bp处扩增出条带,经测序和比对结果证实为CMY-2型质粒AmpC酶。10株产AmpC酶大肠埃希菌接合试验有2株接合阳性,接合子均扩增出CMY-2型条带。药敏结果显示6株产质粒AmpC酶大肠埃希菌对3代头孢菌素、氨曲南和含酶抑制剂的敏感性极低,对亚胺培南和美罗培南均敏感。结论海南地区存在产质粒介导的CMY-2型AmpC酶大肠埃希菌,药敏结果显示对3代头孢菌素耐药率极高,但对亚胺培南和美罗培南均敏感。

[ Objective ] To investigate the genotype characteristics of β-lactamases from plasmid-mediated AmpC of Eseheriehia eoli in Hainan. [ Methods ] A total of 540 clinical nonrepeat isolates of E. eoli were collected from 8 hospitals of Halnan in 2009. They are detected by disc diffusion method for phenotypie screening and three-dimensioned extract test for AmpC β-1aetamases. The plasmid conjugation test was applied to confirm the spread of resistance gene. The genotype of AmpC β-lactamases were detected by polymerase chain reaction （PCR） and DNA sequencing methods. The minimal inhibitory concentrations （MIC） on AmpC β-lactamases producing strains were determined by E-test. [Result] Of 540 isolates, 123 （22.8%） strains had an inhibition ring to eefoxitin of 〈18 mm diameter, 10 （1.9%） strains exhibit a positive three-dimensioned extract test. Conjugation test was positive for 2 of the 10 strains. AmpC β-1actarnases were CMY-2 type confirmed by PCR and DNA sequencing methods. E-test results showed that they are highly resistant to third-generation cephalosporins, but all are sensitive to imipenem and meropenem. [ Conclusions] There are epidemic strains of E. coli producing plasmid-mediated CMY-2 type AmpC β-laetamases in Hainan. They are highly resistant to third-generation eephalosporins but all are sensitive to imipenem and meropenem.