Staphylococcus aureus is a Gram-positive pathogen that causes a variety of diseases including bovine mastitis, which has severe economic consequences. Standard antibiotic treatment causes the selection of resistant strains, leading to a need for alternative treatments such as bacteriophage therapy. 49 S. aureus isolates were obtained from the milk of mastitic cows for use in the screening of staphylococcal phages. Fifteen isolates which tested positive for both coagulase and hemolysin were assayed by PCR for variation in the X region and the IgG-binding region of the protein A gene (spa), in the carboxy-terminal of the coagulase gene (coa) and for presence of enterotoxin C, G, H and I genes. The host range of 52 phages isolated from sewage influent was determined by spot test on the 15 S. aureus isolates and two phages were subsequently chosen for further analysis. ΦSA039 had the widest range, producing clear plaques on 13 of the 15 isolates (87%), while ΦSA012 produced clear plaques on eight (53%) and was the only phage to produce one on a non-mastitic S. aureus strain. Transmission electron microscopy revealed that the phages were of similar size and belonged to the Myoviridae family. Measurement of optical density during co-culture with S. aureus isolates confirmed the breadth of the ΦSA039 host range, and showed that ΦSA012 had a potent lytic capability. ΦSA012-resistant bacteria did not appear in 3 out of 7 isolates tested (43%) after 65 hours’ incubation. These two phages are proposed as candidates for phage therapy of bovine mastitis.
各種検索
サポート
ヘルプ