Study on the Detection of AmpC Enzyme Hyperproduction and Extended-spectrum β-lactamases and its Antimicribial Resistance in Clinical Isolates of Enterobacter Cloacae

Objective To detect the stably derepressed expression of AmpC β-lactamases(AmpC)and extended spectrum β-lactamases(ESBLs)of Enterobacter cloacae,and its antimicrobial activities.Methods 154 clinical strains of Enterobacter cloacae were collected from five hospitals in Xi'an area from January 2004 to June 2005;Modified three-dimensional of cefoxitin/cefiriaxone test were used to detect AmpC and ESBLs respectively;Lirby-Bauer(K-B)method were performed to detect the susceptibility of 16 antimicrobial agents against Enterobacter cloacae.Results The incidence rate of single producing AmpC was 22.73%;the incidence rate of single producing ESBLs was 18.83%;the incidence rate of producing both enzymes was 5.19%;the incidence rate of producing neither AmpC nor ESBLs was 53.25%.Conclusion The study demonstrated that the prevalence of strains producing AmpC and/or ESBLs isolated from patients in Xi'an area was at a higher level compared with other cities in our country;the strains producing AmpC and/or producing ESBLs were multiple-antibiotics-resistant to β-lactamases cephalosporins;the best antibiotics for treatment of infections caused by AmpC-producing strains in Enterobacier cloacae is Imipenem,followed by Cefpirome;the best antibiotics for treatment of infections caused by ESBLs-producing strains is Imipenem,followed by Piperacillin/Tazobactam and Cefoperazone/Sulbatam;hyperproduction of the AmpC β-lactamase and/or ESBLs had been documented as a prevalent mechanism of β-lactam resistance in Enterobacter cloacae.