At each sampling time, 5 g of the seeds were mixed with
25 ml of TSB in a stomacher bag (400 ml; Interscience, St. Nom La
Breteche, France) and pummeled for 1 min. The homogenate was
serially diluted in sterile 0.1% peptone water and surface plated on
tryptic soy agar (TSA; BD/Difco), MacConkey sorbitol (BD/Difco)
agar containing nalidixic acid (50 mg/ml) (MSAN), and dichloran
rose bengal chloramphenicol (DRBC; BD/Difco) agar to determine
populations of TAB, E. coli O157:H7, and MY, respectively, on seeds.
TSA and MSAN plates were incubated at 37 C for 24 h, and DRBC
plates were incubated at 25 C for 5 days before colonies were
counted.