A simple field test for the detection of inhibitory substances in milk supplies

Abstract

A modification of a previously reported non-acid test uses only simple equipment which is normally available at factories for methylene blue testing. The method depends upon the slower reduction of methylene blue by Streptococcus thermophilus during incubation at 45°C. It detects penicillin at a concentration of 0·02 I.U./ml and is sensitive also to oxytetracyline and chlortetracycline.