The effect of casein derivatives on glycine enhancement of β-lactamase production in Enterobacter cloacae ATCC.13047

Abstract

Our earlier work showed that glycine enhancement of class I beta-lactamase production in Enterobacter cloacae ATCC.13047 was greater on Isosensitest Agar than on other laboratory media. In the present study it was demonstrated that Casein Hydrolysate was the constituent of Isosensitest Agar which was necessary for glycine enhancement of beta-lactamase production. Also, a comparison of the effect of casein and casein derivatives on glycine enhancement of beta-lactamase production showed that acid hydrolysis of casein was a prerequisite for glycine enhancement of beta-lactamase production. Enterobacter cloacae ATCC.13047 failed to grow on a medium containing casein, and glycine enhancement of beta-lactamase production did not occur on a medium containing tryptic hydrolysate of casein. The effect on beta-lactamase production of variations in the concentrations of both Casein Hydrolysate and glycine was examined by titration of both components in a chequerboard fashion. Beta-lactamase production was influenced by the concentrations of both Casein Hydrolysate and glycine. This inter-relationship indicated that there was a balance between the concentrations of Casein Hydrolysate and glycine and that alterations in this balance modified beta-lactamase production. The significance of the observations is discussed in relation to the factors which influence glycine enhancement of beta-lactamase production in Enterobacter cloacae ATCC.13047.