Bacteriophages LSA2308 and LSA2366 infecting drug-resistant Staphylococcus aureus: Isolation, characterization and potential application for milk safety

Bacteriophages are considered a promising candidate for controlling food pathogens. In this study, we isolated and characterized S. aureus-infecting bacteriophages, and investigated their potential for antibiotic substitute and bacteriophage cocktail effect in Luria-Bertani (LB) broth and skim milk. Bacteriophages LSA2308 and LSA2366 possessing lytic activity against drug-resistant S. aureus were isolated. The latent period of LSA2308 and LSA2366 was approximately 20 and 10 min, with burst size of 407 and 258 PFU per infected cell, respectively. A combination of LSA2308 (or LSA2366) and 1/2 MIC ampicillin achieved better clearance of S. aureus CR003 in LB broth than treatment with either bacteriophage or ampicillin alone. Biocontrol with 10(5)-10(7) PFU/mL LSA2308 or LSA2308/LSA2366 cocktail was effective in LB broth, whereas it was less active in skim milk. Compared with treatment using 10(5) or 10(6) PFU/mL bacteriophages, the bactericidal efficacy of 107 PFU/mL bacteriophages on single or mixed S. aureus strains in skim milk was the best at 4 and 25 degrees C, revealing a dose-dependent mode. Our study further expands the repertoire of bacteriophages infecting drug-resistant S. aureus, and provides insights into the control of S. aureus in milk production chain.

Automated summary

Bacteriophages LSA2308 and LSA2366 showed lytic activity against drug-resistant S. aureus, and combined with ampicillin achieved better clearance in LB broth. In skim milk, a concentration of 10^7 PFU/mL bacteriophages exhibited the most effective bactericidal efficacy against S. aureus strains.