Antimicrobial Activity
Pathogen Inhibition
The capability of the strains to inhibit a group of foodborne pathogens was determined using an agar spot test as described by Ripamonti et al. (2011). Overnight test cultures were spotted (2 µL) on the surface of modified MRS agar (without ammonium citrate and sodium acetate) and incubated anaerobically for 24 h at 30°C. Cells were then inactivated with chloroform for 30 min. Escherichia coli ATCC 25922, Salmonella enterica var. Enteritidis ATCC 13076, Staphylococcus aureus ATCC 25923, and Listeria monocytogenes ATCC 15313 were used as indicators. A 100-µL volume of an overnight culture of each indicator was mixed with 10 mL of brain heart infusion (Difco) soft agar (0.7%), and poured onto MRS agar plates. These were incubated aerobically at 37°C for 24 h. Lactobacillus acidophilus ATCC 4356 was used as a negative control. Inhibition but no clear-cut halo or a halo 1 mm was scored as + (positive); and an inhibition zone between 2 and 5 mm surrounding the colony was recorded as ++.