400 (Interscience, Saint Nom, France). Subsequently, the samples
were serially diluted using sterile saline solution. The media used to
enumerate E. coli O157:H7, S. Typhimurium, and L. monocytogenes
were tryptic soy agar, nutrient agar, and tryptic soy agar containing
0.6% yeast extract (Difco), respectively. We spread 100 mL of each
dilution on plates containing the appropriate medium; this was
performed in triplicate. The plates were incubated at 37 C for 48 h;
the colonies were counted after the incubation period.