In vitro activity of cefmetazole against extended spectrum β-lactamases producing Enterobacteriaceae isolates

Objective To evaluate the in vitro antimicrobial activity of cefmetazole against extended spectrum β-lactamases(ESBLs)producing Enterobacteriaceae isolates.MethodsA total of 523 strains of E.coli,K.pneumoniae,K.oxytoca and P.mirabilis were isolated from clinical specimens.Antimicrobial susceptibility testing was done by agar dilution method.The results were assessed according to the Clinical and Laboratory Standards Institute(CLSI)and compared with selected antimicrobial agents.ResultsOf the 523 strains tested,291 produced ESBLs,7 produced AmpC,40 produced both ESBLs and AmpC,and 182 produced neither ESBLs nor AmpC.Cefmetazole had excellent antibacterial activity against both ESBLs-positive and ESBLs-negative strains,which was 2 to 4 times higher than cefoxitin,but lower than cefminox.Cefmetazole was very stable against ESBLs,but less stable against AmpC.Strains producing AmpC were much more resistant to cefmetazole.The activity of cefmetazole against ESBLs-producers was better than semisynthetic penicillins,and first-,second-,third-and fourth-generation cephalosporins,as well as ampicillin-sulbactam,cefoperazone-sulbactam and piperacillin-tazobactam,but inferior to imipenem,meropenem and panipenem.The activity of cefmetazole was slightly higher than or comparable to the aminoglycosides and fluoroquinolones tested.ConclusionsCefmetazole is stable against ESBLs.Cefmetazole exhibits good activity against both ESBLs-producing and non-ESBLs-producing strains.These results indicate that cefmetazole is one of the options for the treatment of infections caused by ESBLs-producing Enterobacteriaceae strains.