Undiluted suspensions (0.25 ml in quadruplicate
and 0.1 ml in duplicate) and suspensions (0.1ml in duplicate) serially
diluted in 0.1% PWwere surface plated onMacConkey Sorbitol agar
(MSA, BBL/Difco) and incubated at 37 °C for 24 h before counting colonies.
The remaining mixtures (coupons, 0.1% PW or DE neutralizing
broth, and glass beads)were combinedwith 100 ml of TSB and incubated
at 37 °C for 24 h to enrich for E. coli O157:H7.