INDUCTION OF STAPHYLOCOCCAL PENICILLINASE BY BENZYLPENICILLIN: EFFECT OF pH, CONCENTRATION OF FERROUS ION AND INDUCER, AND DURATION OF EXPOSURE OF CELLS TO INDUCER

Abstract

Induction of staphylococcal penicillinase by benzylpenicillin: effect of pH, concentration of ferrous ion and inducer, and duration of exposure of cells to inducer. J. Bacteriol. 86:717-727. 1963.-The kinetics of induction of penicillinase by benzylpenicillin in exponentially multiplying Staphylococcus aureus strain 55-C-1 were shown to vary with the pH. At pH 7.3 in the absence of free inducer, the rate of increase of penicillinase activity rapidly declined and came to a halt. At pH 5.4 to 5.5 and in the presence of optimal concentrations of Fe++, the penicillinase activity of the induced culture increased linearly with time for 2.5 or more generations, but the rate of increase usually declined eventually. Evidence was advanced to support the concept that the acidic pH and optimal Fe++ concentration maintain the induced formation of enzyme. The induced increase in penicillinase activity appeared 3 to 4 min after the addition of benzylpenicillin. The degree of induction of penicillinase varied with the duration of exposure of the staphylococci to the inducer and with the concentration of inducer. Maximal induction under our conditions was attained by exposure for 15 min to benzylpenicillin at an initial concentration between 0.6 and 2 units/ml. Although the inducibility of staphylococcal penicillinase has been known for some time (Geronimus and Cohen, 1957; Steinman, 1961; Crompton et al., 1962), more information on the characteristics of this system, comparable with that developed for classical systems such as penicillinase in Bacillus cereus and f-galactosidase in Escherichia coli, has been lacking. In this paper, we present results of studies of the kinetics of induction of staphylococcal penicillinase. We have found that the kinetics of induction of this enzyme in exponentially multiplying cultures of Staphylococcus aureus vary markedly with pH and Fe concentration. At an acidic pH in the range from 5.4 to 5.5 and a favorable Fe concentration, penicillinase activity increases linearly with time in the absence of free inducer, in a fashion kinetically similar to but usually not so prolonged as that described by Pollock (1950) for B. cereus. Other aspects of induction in this system, including the effects of time of exposure of cells to inducer, are also presented. MATERIALS AND METHODS Organisms. S. aureus strain 55-C-1 (Geronimus and Cohen, 1957) was the routine test organism. Drops of overnight broth cultures taken up on porcelain beads and then desiccated over silica gel served as routine inocula. The dried beads, stored at 4 C, were used for periods up to 6 months. A few experiments were repeated with several other penicillinase-producing strains of S. aureus to test the generality of the observations. These strains were stored and inoculated from nutrient agar slants. Media. Cultures were grown in tryptic digest broth (TD), lot no. 003607 (BBL), unless otherwise stated. Several other lots failed to sustain growth at pH 5.5. It was eventually found that acetic acid added to the tryptic meat digest during t...

Gratuitous Synthesis of β-Lactamase in Staphylococcus aureus

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Induction of Penicillinase by Staphylococci In Vitro and In Vivo

“…There was also no significant difference between induction ratios in experiments carried out at 37 and 39 C. However, a decrease in induction ratio was observed at temperatures below 37 or at 41 C. DIscussIoN Geronimus and Cohen (4) and others (6,12) have shown that the penicillinase activity of penicillin-resistant strains of S. aureus is greatly increased by exposure to penicillin in vitro for brief periods of time under conditions precluding significant multiplication of bacteria. These observations, indicating that staphylococcal penicilhinase is an inducible enzyme, led to studies to determine the degree to which induction of enzyme could be demonstrated in vivo during the course of experimental staphylococcal infections.…”

“…Induction of penicillinase in leukopenic mice with peritoneal staphylococcal infectionz Group If................... 3.0 X 108 Group 2f..................Group 3Y ................... 3.Group 4f..................Number of cells of Staphylococcus aureus AZ injected intraperitoneally in each mouse.Collected 6 hr after administration of procaine penicillin to the groups of treated mice. Units of potassium penicillin G degraded per 106 staphylococci 6. Procaine penicillin G, 30,000 units intraperitoneally per mouse.…”

Rapid, inexpensive method for specific detection of microbial beta-lactamases by detection of fluorescent end products

“…For example, the routine 1-lactamase nitrocefin tests of staphylococcal isolates require a noninhibitory concentration of a semisynthetic penicillin as an inducer for the enzyme (8). In our fluorescent spot test method, with sufficient incubation time (e.g., -15 min; Table 2) amnpicillin could serve not only as a substrate but also as an inducer for these gram-positive bacteria of clinical importance (11). The potential of this method for testing clinical isolates for 3-lactamases which may have a predominance of penicillinase or cephalosporinase activity deserves further evaluation.…”