Bacteriophage performance against Staphylococcus aureus in milk is improved by high hydrostatic pressure treatments

The combined effect of bacteriophages, vB_SauS-phi-IPLA35 (phiIPLA35) and vB_SauS-phi-IPLA88 (phiIPLA88), and high hydrostatic pressure (HHP) on Staphylococcus aureus Sa9 was evaluated in pasteurized whole milk under a simulated cold chain break, which was simulated by incubation of milk at 25 °C for 48 h. Four-hundred MPa was found to be the most suitable pressure to be used in combination with these phages. Two different levels of staphylococcal initial contamination (1 × 104 and 1 × 106 CFU/mL) were tested. A synergistic effect between HHP and phages was observed in both cases. Compared to each single treatment, the combined treatment was able to reduce the initial S. aureus contamination below the detection limit (< 10 CFU/mL). Bacteriophage performance in pressurize milk against S. aureus enabled milder hydrostatic pressure treatments, therefore phages can be regarded as a valuable hurdle on minimally processed food.