When colonies did not
form on MSA plates, the enriched suspension was streaked on MSA
plates and incubated at 37 °C for 24 h. Colonies formed on MSA plates
were randomly selected and tested using the E. coli O157 latex agglutination
test (Oxoid, Basingstoke, UK) to confirm E. coli O157. The detection
limits of E. coli O157:H7 by direct plating and enrichment were
1.5 log CFU/coupon (30 CFU/coupon) and 0.0 log CFU/coupon (1 CFU/
coupon), respectively.