4.5. The Multiplicity of Infection (MOI) of Phage Henu2

To determine the optimal MOI, the logarithmic phase S. aureus and a serial dilution of Henu2 were co-incubated in 1.5 mL polypropylene tubes. The ratio of bacteriophage and S. aureus was adjusted to 10, 1, 0.1, 0.01 and 0.001 respectively. Then, the mixture was cultured in a shaking incubator at 30 °C, for 4 h. Subsequently, the mixture was centrifuged at 10,000 rpm for 1 min and filtered to remove the host bacteria. Then the bacteriophage titer was determined using the double-layer agar method. The mixture with a ratio of Henu2 to S. aureus with the highest phage titer value was considered the optimal multiplicity of infection (OMOI). A total of 3 replicates were performed.