Inducibility of ?-Lactam Antibiotics to AmpC ?-Lactamase in Enterobacter cloacae / 中华医院感染学杂志

ABSTRACT

OBJECTIVE To analyze the resistance of Enterobacter cloacae AmpC ?-lactamase with/without being induced by imipenem(IMP),cefepime(FEP),ceftriaxone(CRO) and aztreonam(ATM).The ampD genes of mutant strains were sequenced. METHODS Five wild type strains and 5 hyper-inducible type strains of E.cloacae were selected and induced by the tested antibiotics in vitro.At the same time,antibiotic susceptibility tests,3-D test,isoelectric focusing(IEF) and inhibit experiment were detected to identify hyper-producing AmpC ?-lactamase.ampD Gene sequencing was preformed in part of mutant strains. RESULTS There wasn′t obvious alteration in MIC with IMP,FEP,CRO and ATM for wild type strains whether they were induced or not.But,for the hyper-inducible type,there was apparent increasing in MIC after antibiotics inducing,especially CRO and ATM,up to 10.7-128 times.The DNA sequences analysis in the mutation strains showed there existed the replacement of the single base in multiple sites,and a few sites of amino acid were altered. CONCLUSIONS Mutant sites in ampD gene sequences are identical even though antibiotics as inducer are different.