4.3.1. Quantification

The quantification of BPABΦ1 was performed using the double-layer agar overlay (DLAO) method and measured in terms of the phage titer value (PFU/mL). Briefly, 1 mL of each BPABΦ1 sample and bacterial host (200 µL of 1.0 optical density (OD)) was added to the separate soft agar (0.75%) in molten condition. The phage-host suspension in soft agar was overlaid on solidified bottom agar in 90 mm petri plates. Plates were then gently swirled, dried at room temperature for 10 min, and incubated overnight at 37 °C. The next day, the BPABΦ1 titer was enumerated by the following equation [32];

After getting plaques from the DLAO assay, the plaque morphology was characterized based on the plaque diameter, a halo zone around the plaques, and bacterial clearance [33,34].