EVALUATION OF VARIOUS PLATING MEDIA FOR ENUMERATION OF PSYCHROTROPHIC BACTERIAL IN MILK*

40 random samples of market milk sold in Assiut City markets were collected and examined bacteriologically for enumeration and isolation of psychrotrophic bacteria using heart infusion agar, standard methods agar and trypticase soya agar.
Our study revealed that heart infusion agar is more reliable for direct enumeration of psychrotrophic bacteria if compared with standard methods agar and tryticase soya agar. Moreover it is apparent that media which contain crystal violet (2 mg/Litre) is evaluated as more rapidly in order to obtain psychrotrophic count.
The mean psychrotrophic count on heart infusion agar, standard method agar, and trypoticase soya agar with crystal violet were 7.02x10°, 2.2x106 and 4.5x 106 respectively, while without crystal violet were 13.8x106, 3.5x106 and 4.66x106 respectively. Pseudomonas species, Alcaligenes faecalis, Acinetobacter antiratus, Flavobacter, coliforms, proteous species and Serratia species were isolated in different percen tage.