[Determination of the beta-lactamase-inhibiting capacity of different compounds by using a penicillinase-forming strain of Staphylococcus aureus 5A].

A diffusion method with the use of a penicillinase-forming strain of Staph. aureus 5A was applied to determination of the beta-lactamase inhibitory activity of various compounds. The method is based on measuring the difference in the size of the growth inhibition zones of the staphylococci on trays with and without benzylpenicillin. The method is rather informative. However, a nonspecific secondary beta-lactamase inhibitory effect of high doses of the antibiotic inhibitors of the protein synthesis is possible. Two diffusion methods for determination of the beta-lactamase inhibitory activity of various compounds, i.e. the indicator method based on the direct contact of crystalline penicillinase with the experimental substrate and the method using a penicillinase-producing strain of Staph. aureus 5A and various beta-lactamase-producing strains of bacteria without preliminary obtaining of beta-lactamase preparations were compared. It was shown that the indicator method was more rapid, simple and accurate. Still, it did not provide determination of the antibacterial activity of the compounds. It is advised to use both methods for screening various compounds and studying their beta-lactamase inhibitory activity.