On each of 55 days, split pig carcasses leaving a carcass cooling process were selected at random for sampling and enumeration of generic Escherichia coli by three methods. Method A involved swab sampling with a single, cellulose acetate sponge, of three specified sites on one side of each selected carcass, with each swabbed area of 100 cm 2 being delimited by a template, and enumeration of E. coli by a plating technique with a level of detection of 1 cfu 24 cm −2 , as specified by the US Department of Agriculture (USDA). Method B involved swabbing the same three sites as in method A, but each site was swabbed with a separate gauze swab over an undelimited area of approximately 100 cm 2 . The three swabs from each carcass were combined for the enumeration of E. coli as in method A. Method C involved swabbing a single, randomly selected site on each selected carcass with a gauze swab as in method B, and enumeration of E. coli by a hydrophobic grid membrane filtration technique with a level of detection of 1 cfu 100 cm −2 . All three methods yielded E. coli with similar frequency and with the recovery of similar numbers of cfu. Therefore, method B can be regarded as equivalent to method A for demonstration of compliance with the USDA criterion for acceptable E. coli contamination of cooled pig carcasses. However, because of the difference in the sites that are sampled method C could be regarded as equivalent to method A only if an E. coli criterion appropriate to method C but equivalent to the USDA criterion can be recognized by regulatory authorities.
