Isolation and identification, biological characterization of Staphylococcus aureus phage and its application in milk

Staphylococcus aureus is one of the important pathogens that cause food contamination worldwide, and poses a great danger to people. The common treatment is antibiotic therapy; however, the misuse of antibiotics has led to the continuous emergence of drug-resistant strains. Therefore, new antibacterial methods need to be explored. In this study, a lytic S. aureus phage (named SP-CmSa-11) was isolated from dairy farms which belongs to the Myoviridae phage family. The optimal multiple of infection of SP-CmSa-11 is 0.1, and the host range included 7 strains of mastitis cow-derived S. aureus, 12 strains of animal-origin methicillin-resistant S. aureus, 1 strain of S. xylosus, 1 strain of S. epidermidis and 1 strain of Enterococcus faecalis. SP-CmSa-11’s burst period was 40 min, and the burst size was about 130 PFU/cell. SP-CmSa-11 was inactivated after 10 min in a water bath at 70 °C, and the pH tolerance of SP-CmSa-11 ranges from 4 to 10 in 2 h. It’s insensitive to chloroform and ultraviolet radiation. The total genome length of SP-CmSa-11 is 45 816 bp. The G + C content is 27.23%, and has 59 putative open reading frames. SP-CmSa-11 showed good antibacterial effects in vitro and milk. These results suggest that SP-CmSa-11 may be a promising alternative therapy for food contamination caused by S. aureus.