PRODUCTION OF AMIDASE AND BETA-LACTAMASE BY BACTERIA.

Abstract

SUMMARY: Fresh clinical isolates of Gram-positive and Gram-negative bacteria were tested for the production of β-lactamase and amidase. Techniques for identifying and studying the latter enzyme are described, in relation to its action upon penicillins and other substrates. Various commensal and pathogenic Gram-negative bacilli produce a ‘pen-amidase’ of relatively narrow specificity, though no species invariably produces it. A specific pen-amidase was not formed by the Gram-positive bacteria examined, though nonspecific amidases were present. Escherichia coli and paracolon bacilli produced pen-amidase more often than β-lactamase but the Klebsiella-aero- genes group did the reverse. Among other organisms, enzyme production was very variable but absence of either enzyme did not necessarily connote sensitivity of an organism to any penicillin. Administration of penicillin to a patient promotes colonization of the gut and oropharynx by β-lactamase- forming coliforms, but not of amidase-forming organisms. There is a strong association between resistance to the penicillins and formation of β-lact- amase by an organism; with pen-amidase, the association is less strong. Neither enzyme accounts completely for bacterial resistance to the penicillins, even within any one species of organism, but the lower resistance of coliforms to ampicillin may be related to the lesser susceptibility of this derivative to amidase.