[Characteristics of determining the microbial contamination of penicillin series antibiotic powders and tablets].

Optimal conditions for determination of microbial contamination of drugs were studied on artificially contaminated powders and tablets of phenoxymethylpenicillin, ampicillin, oxacillin and dicloxacillin. The method of membrane filtration was the best for determination of the microbial contamination of the powders. However, it was not possible to wash out completely the antibiotic from the membrane filter. To prevent this it was necessary to add penicillinase into the nutrient medium onto which the filter was put for providing the microbial growth. For determination of microbial contamination of tablets direct plating of 3 per cent suspension of the tablet mass onto the surface of the nutrient medium with penicillinase was the best.