Bacteria, including Salmonella, have been shown to attach firmly to poultry skin and meat. Neither fimbriae, flagella, nor electrostatic attraction seem to play a significant role in the mechanism of attachment. Bacterial cells (95%) were shown to be initially entrapped in a water film on the skin, then to migrate to the skin with prolonged immersion in a bacterial cell suspension. Using electron microscopy it was shown that bacteria appear to be entrapped in ridges and crevices which become more pronounced in the skin and muscle following water immersion. This may make bacteria on carcasses inaccessible to bactericides. It was shown that bacteria are firmly attached to poultry skin before broilers arrive at the plant and that high numbers are still recovered after 40 consecutive whole carcass rinses of a single carcass. It was further shown that Salmonella are not always recovered in the first whole carcass rinse and that this method of sampling could result in false negative reports for Salmonella incidence.

Levels of aerobic bacteria, Enterobacteriaceae, and the incidence of Salmonella were determined at six sampling points in a commercial processing plant: (1) pre-scald (at bleed line); (2) post-scald; (3) post-pick (4) post-evisceration; (5) pre-chill (after the final washer); and, (6) post-chill. The level of aerobic bacteria and Enterobacteriaceae on broiler carcasses was reduced significantly by commercial processing procedures, but cross-contamination still occurred. There was no increase in Salmonella incidence on carcasses from the five sampling points starting with the kill line through the final washer. There was a significant increase in Salmonella incidence on carcasses exiting the immersion chiller, indicating that this may be the point of most significant cross-contamination in broiler processing plants.

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