Microbiological assay of antibiotics in Elgyptian Dairy products

Abstract

Sensitive strains of Streptococcus themophilus were used for assay of antibiotics in Egyptian dairy products. It was found that the yeast extract lowered the sensitivity of the above strains to penicillin. It was found that 3.1% of milk samples in Alexandria were positive to antibiotics Both of examine? pasteurized, dried, evaporated, sweetened condensed, sterilized and UHT milk were founa to be negative. The high sensitivity of S.thermopnilus starter to NaCl gave false results. The penicillin remained detected for three days in the milk after being ingected cows suffering from mastitis. Adding of penicillin ranged 0.05–0.30 IU/ml milk caused an apparent effect. The cells showed tendency to be longer and thicker than unexposed cells. Penicillin gave stability in both pasteurized and boiled milk. When Bacillus stearotherinophilus used it was found that the liter organism more sensitive than the former for the assay of antibiotics.