The application of molecular typing techniques to HACCP

Cross-contamination of carcasses and equipment during pork processing

AIMS

The cross-contamination events within a commercial pork processing line were examined by a combination of ERIC-PCR DNA fingerprinting of Escherichia coli and plate counts.

METHODS AND RESULTS

Sponge sampling of environmental surfaces and carcasses was performed over an 8-h processing period. Prior to the start of processing the scraper and dry polisher blades were found to harbour substantial Enterobacteriaceae and Escherichia coli populations. From plate count data the key cross-contamination site for the transfer of bacteria between carcasses occurred during evisceration. However, DNA fingerprints of representative E. coli isolates identified that genotypes initially present on the scraper/dry polisher became distributed on wet polisher blades, band-saw and butcher's hands despite a singeing step being performed post dry polishing. A high proportion of E. coli on post-eviscerated carcasses could be traced to down-stream (pre-singe) environmental contact surfaces.

CONCLUSIONS

DNA fingerprinting has demonstrated that E. coli and potential enteric pathogens can be transferred between pork carcasses throughout the processing line. In this respect scalding and singeing cannot be relied upon to control cross-contamination of enteric bacteria between carcasses.

SIGNIFICANCE AND IMPACT OF THE STUDY

Sole reliance on indicator organism counts to identify cross-contamination events as currently advocated is limited.