Isolation and Characteristics of Bacteriophages for Staphylococci of Bovine Mastitis

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Abstract
Methods were developed for the isolation of staphylococcus bacteriophage from milk. This involved the incubation of milk samples for 18 hrs. at 37[degree]C, adding sufficient rennet extract to curdle the milk and continuing incubation at room temp. for 4 days. The whey is then filtered through Seitz and Chamberland-Pasteur filters and added to broth cultures of phage-susceptible staphylococci. The usual procedures for the detection and isolation of phage were then followed. A pour plate technique using semisolid agar (0.5-0.8%) was devised which facilitated the counting and morphological study of phage plaques. Milk samples from a herd of 20 cows showing evidence of staphylococcal mastitis were examined and staphylococcus phages were isolated from 7 of the 20 cows. The bovine phages isolated resembled phages from human sources in most respects. The plaque size and a certain heat lability of some of them were the only noticeable differences. All attempts to show specificity of lysis failed; phages from milk lysed staphylococci of both bovine and human origin and phages from human sources did likewise. There was no correlation between susceptibility to lysis and biochemical or toxin-producing characteristics. Animal expts. with kittens and rabbits demonstrated the effects of phage therapy under varying conditions and suggested that treatment of staphylococcal mastitis with phage may be of little value.

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