Detection of AmpC β-lactamases and analysis of its drug resistance in gram-negative bacilli

Objective To investigate the incidence of clinical isolates of gram-negative bacilli producing AmpC β-lactamases and its drug resistance.Methods AmpC β-lactamases were identified by three-dimensional test;and the susceptibilities of antimicrobial agents were detected by KirbyBauer disk diffusion test.Results Of 236 gram-negative bacilli,29 strains produced β-lactamases with three-dimensional test,17 strains(7.2%) only had AmpC β-lactamases,8 strains(3.4%) only had extended-spectrum beta-lactamases(ESBLs),2 strains(0.8%) had both ESBLs and AmpC,2 strains(0.8%) had no AmpC-ESBLs β-lactamases.Therefore,19 strains produced AmpC β-lactamases,the frequency of AmpC β-lactamases was 8.1%.The susceptibility test showed that the drug resistant rate of AmpC producer was higher than non-AmpC producer except imipenem and cefepime.Conclusion The frequency of AmpC β-lactamases was 8.1% in the hospital.Multiple drug resistance appeared in AmpC producer.The fourth-generation cephalosporins and carbapenems should be considered to treat the infection caused by AmpC producer at first.