2.2. Screening for Antibacterial Activity

A screening was performed according to a deferred antagonism test [46]. Staphylococcal strains were prestreaked on MSA, after which a single colony was picked up to inoculate 5 mL of BHI broth. After overnight incubation, 10 µL of the inoculated BHI was applied as a central streak (width of 5 mm) on BHI agar (1.5% w/v) and incubated for 24 h. Afterwards, the agar medium was flipped and overlayed with soft BHI agar (0.7% w/v) inoculated with 100 µL of an overnight grown indicator strain. All incubations were performed at 30 °C. Antibacterial activity was scored according to the width of the inhibition zone (IZ) measured from the central streak; 0 = no inhibition, 1 = IZ ≤ 1 mm, 2 = 1 mm ≤ IZ ≤ 4 mm, 3 = 4 mm ≤ IZ ≤ 8 mm, and 4 = IZ ≥ 8 mm. The complete set used in the screening can be found in Supplementary Table S2.