ANTIBIOTIC ASSAY MEDIUM NO. 4 (as per USP)

This dehydrated culture medium is suitable for plate counts in pharmaceutical and related products and for the microbial assay and detection of antibiotics like penicillin in milk. This medium is formulated in accordance to the specifications and procedures listed by the Food and Drug Administration and USP.This medium is identical numerically with name assigned by Grove and Randall.
Generally presence of penicillin in milk is detected by the cylinder plate method, using Micrococcus luteus as the test organism, and by paper disk method, using Bacillus stearothermophilus . The cylinder plate method is recommended as the standard for quantification of ?-lactam residues. A description of the cylinder plate method for detecting penicillin in dry powdered milk is given by Kramer et al.. The same basic procedure is also recommended to the assay of penicillin in fluid milk.
Freshly prepared plates should be used for antibiotic assays. The use of this medium assures well defined zones of the test organism. All conditions in the microbiological assay must be controlled carefully. The use of standard culture medium in the test is one of the important steps for obtaining good results.

for detection of Penicillin in milk and for microbiological assay of di?erent antibiotics