High AmpC ?-Lactamases-producing Escherichia coli Isolated from Hospital Infection Patients:A Molecular Study / 中华医院感染学杂志

ABSTRACT

OBJECTIVE To investigate the occurrence and the genotype character of AmpC ?-lactamases-producing Escherichia coli isolated from the Second Hospital affiliated to Harbin Medical University.METHODS K-B disk diffusion test and FOX(≤17mm) test were used as initial screen tests to detect the clinical isolates;AmpC ?-lactamases were confirmed by three-dimentional extract tests;multiple-PCR was used for detecting plasmid-mediated AmpC gene and their genotypes were determined by DNA sequencing;the regulator genes of high producing AmpC isolates of E.coli were cloned to pUCm vectors and sequenced,the difference among them was analyzed by blast method.RESULTS Among total 586 E.coli clinical isolates,10 isolates(1.70%) resisted to cefoxitin;three-dimensional extract tests were positive for all 10 isolates;4 isolates of E.coli were plasmid-mediated DHA-1 type AmpC ?-lactamases by using multiplex PCR and DNA sequencing;6 isolates of chromosomal high level AmpC ?-lactamases-producing E.coli were sequenced and contrasted to that of E.coli K12,showed that they were gene polymorphism.CONCLUSIONS E.coli clinical isolates producing high level AmpC ?-lactamases not only acquire plasmid-mediated DHA-1 AmpC ?-lactamases but also cause by chromosomal ampC promotor or attenuator gene mutations in our hostiptal.