Characteristics of bacteriophages of the Staphylococcus aureus variant bovis

Abstract

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.

Effect of Phage SAvB14 combined with antibiotics on Staphylococcus aureus variant bovis

“…Those antibiotics were chosen depending on the mechanism of their action: inhibitor of protein synthesis (gentamicin, tetracycline), inhibitor of DNA synthesis (enrofloxacin) and inhibitor of synthesis of cellular wall (сeftriaxone). Previous studies revealed that 8 hours following the contact of virus and Staphylococcus, microbial cells began to undergo lysis, which decreased their number 10-fold, and 32 h after the phage started to contact the biofilm, no bacterial cells were generating at all (Horiuk et al, 2020). In this study, we determined the number of vital bacteria in 24h of biofilm of S. aureus var.…”

“…Earlier described Phage SAvB14 (Horiuk et al, 2020), as a specific staphylococcus bacteriophage, is efficient in destroying biofilms developed by S. aureus var. bovis in cows' mastitis.…”

“…Efficiency of mastitis treatment of dry cows using antibiotics reached 78% (Dingwell et al, 2003), while the efficacy of those same drugs was 20-40% lower in the period of lactation (Linder et al, 2013). Despite the fact that the situation with antibioticresistance of pathogens in Ukraine is escalating, doctors cannot abandon the use of antibiotics completely (Zazharskyi et al, 2019(Zazharskyi et al, , 2020Horiuk et al, 2020).…”

Sensitivity of Staphylococcus aureus cultures of different biological origin to commercial bacteriophages and phages of Staphylococcus aureus var. bovis

“…This study complements our earlier data on laboratory studies of phages of S. aureus var . bovis , including their morphology, lytic activity, and the effect of Phage SAvB14 on staphylococcal biofilms [ 3 , 6 , 26 ]. Prototypes of a drug based on Phage SAvB14 have been created, and clinical trials are underway.…”

“…The increasing spread of antibiotic resistance among clinical isolates of Staphylococcus aureus is a major problem in human and veterinary medicine [ 1 - 3 ]. The genus Staphylococcus includes commensals and pathogens in both humans and animals [ 4 ].…”