Characteristics of bacteriophages of the Staphylococcus aureus variant bovis

Bacteriophages may be an alternative method of treatment for antibiotic-resistant bacteria, including mastitis in cows. Our study describes the initial isolation and bacteriological activity of bacteriophages, circulating on dairy farms, the against S. aureus var. bovis. Samples of cow's milk secretions with signs of mastitis and sewage water were used as the study material. The isolation and production of pure bacteriophage lines were performed according to the double agar method. The method of studying a single cycle of phage reproduction was used to determine the duration of the latency period. Determination of the spectrum of the lytic activity of bacteriophages against the clinical isolates of the microorganisms was carried out by the drop method. As a result of the research, four phages, specific for S. aureus var. bovis were isolated: Phage SAvB07, Phage SAvB08, Phage SAvB12 and Phage SAvB14. The negative colonies of the isolated phages were 1-2 mm in size, rounded with clear edges, with varying degrees of transparency. The latency period of Phage SAvB14 was 35 min, with the number of active virions increasing by 8 orders. In the study on growth curves of other bacteriophages, taken in the experiment, the latency period was more than 35 min, and their titre increased by only two orders. Phage SAvB07, Phage SAvB08 and Phage SAvB12 were able to lyse the bacterial strains of S. aureus var. bovis in 25-45.6% of the cases (low lytic activity), whereas Phage SAvB14 lysed 94.1% of S. aureus strains were isolated from the cows. Studies have shown that among the bacteriophages we have studied, Phage SAvB14 with a short latency period has the best lytic action on the culture S. aureus var. bovis. The resulting bacteriophage strain can be used to create a bacteriophage-based drug for the treatment of mastitis in cows.