Inducible -lactamase in Enterobacter

Abstract

Production of [beta]-lactamase by 9 strains of the genus Enterobacter (eight Enterobacter cloacae, one E. aerogenes) was studied to determine its inducibility. Induction was observed with benzylpenicillin (500 [mu]g/ml) in all except one strain. Cultures were examined to locate the enzyme; in exponential growth the enzyme was cell-bound, and in stationary phase cultures much of it was in the culture medium. Maximum enzyme activity was only demonstrated after cell-breakage. Substrate profiles of crude enzyme preparations were examined and it was observed that the enzymes were 20-80 times more active against cephalosporins than against benzylpenicillin. One strain of E. cloacae produced 2 [beta]-lactamases, an inducible cephalosporinase and a constitutive peni-cillinase.