Reduced Contamination of Pork Carcasses with Hygiene Indicator Bacteria, ESBL/AmpC-producing Escherichia coli, Salmonella spp. and Yersinia enterocolitica by Alternative Removal of the Pluck Set during Slaughter

Introduction:  Pigs are well-known, asymptomatic carriers of pathogenic and antibiotic resistant bacteria, which may contaminate pork carcasses during slaughter. In particular, opening the oral cavity during the removal of the pluck set (i.e. lungs, heart, liver, and tongue) is a potential risk for spreading bacteria over the pork carcass.

Purpose:  This research aimed to compare carcass contamination between pigs from which the pluck set was removed following standard procedures and pigs froom which the pluck set was, alternatively, removed (leaving the tongue and highly contaminated tonsils inside the unopened oral cavity).

Methods:  In two Belgian slaughterhouses, 20 carcasses (10 slaughtered normally and 10 using the alternative method) from 12 pig batches, were sampled, after removal of the pluck, by swabbing (100 cm²) the elbow, throat, and sternum. Samples were analyzed using direct plating to quantify the total aerobic count, Enterobacteriaceae and Escherichia coli, and to determine the presence of ESBL/AmpC-producing E. coli, Salmonella spp., and Yersinia enterocolitica.

Results:  Average total aerobic counts for throat samples ranged, between batches, from 2.1 to 3.8 log₁₀ CFU/cm² , with mean reductions up to 0.6 log₁₀ CFU/cm² when using the alternative method compared to standard procedures. Median throat Enterobacteriaceae and E. coli numbers varied, between batches, from 0.6 to 2.8 log₁₀ CFU/cm² and 0.4 to 2.3 log₁₀ CFU/cm², respectively, with maximal mean reductions of 1.0 log₁₀ when applying the alternative method. The proportions of Salmonella spp. and Y. enterocolitica positive throat samples were equal for both slaughtering methods and pathogens (1.7%). The presence of ESBL/AmpC-producing E. coli in throat samples ranged from 3-16%, with up to three-fold reductions for the alternative method. Similar results were seen for other carcass areas.

Significance: This alternative slaughter method requires only minimal adaptations in the slaughterhouse, but improved the microbial quality and safety of pork carcasses.