Production of Amidase and  -Lactamase by Bacteria

Abstract

SUMMARYFresh clinical isolates of Gram-positive and Gram-negative bacteria were tested for the production of p-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 p-lactamase but the Klebsiella-aerogenes 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 p-lactamaseforming coliforms, but not of amidase-forming organisms. There is a strong association between resistance to the penicillins and formation of p-lactamase 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.

Cephalosporinase Activity in Bacteroides fragilis

“…Our findings are at variance with previously published information about #-lactamase in B. ragilis (7,12,17) in that penicillinase activity was not demonstrated in our strains. This difference could be explained if (i) penicillinase is either not present in all strains or is present in very small amounts or (ii) the activity of the enzyme is dependent upon the maintenance of its active configuration by a reduced environment.…”

“…Clinically important anaerobic organisms of the genus Bacteroides, which generally are resistant to many $-lactam antibiotics, have previously been studied for enzymes which inactivate these drugs, but the findings reported have been conflicting. Garrod (5) showed penicillinase-like activity in two strains of B. fragilis, but Holt and Stewart (7) were unable to demonstrate inactivation of penicillin in eight strains of Bacteroides species. Pinkus et al (17) studied 40 strains of Bacteroides of various species and showed inactivation of penicillin by 16, of ampicillin by 11, and of oxacillin by 2.…”

Characterisation of a -Lactamase Obtained from a Strain of Bacteroides Fragilis Resistant to -Lactam Antibiotics

“…Studies on the ,6-lactamase of B. fragilis Holt and Stewart (1964) found neither B-lactamase nor amidase activity in eight unspecified strains of Bacteroides, but Garrod (1955) suspected penicillinase activity in 2 of 8 isolates of B. fragilis. Furthermore, Pincus, Veto and Braude (1968) found that 5 of 18 isolates of B. fragilis destroyed benzylpenicillin and 2 of 18 destroyed ampicillin in a microbiological test system, and that the ability to destroy these two penicillins tended to be associated with a high degree of resistance to these antibiotics.…”

In Vivo Protection of Fusobacterium necrophorum from Penicillin by Bacteroides fragilis

“…Attempts to detect f,-lactamase production by B. fragilis cells have been successful in some cases but not in others. Holt and Stewart (10) found no ,B-lactamase or amidase activity in eight strains of Bacteroides. However, Garrod (7), Pinkus et al (12), and Anderson and Sykes (1) fragilis could inactivate the penicillin in its environment, it might also be able to protect penicillin-susceptible organisms present with it in a mixed infection.…”