Journal of Food Protection

In recent years, the role of Listeria monocytogenes as a foodborne pathogen in public health has increased. Its presence poses a risk for humans, especially in ready-to-eat foods, such as ham. Understanding the presence and distribution of Listeria spp. on swine carcasses meant for Italian dry-cured hams can be a useful tool to improve food safety. This study assessed the distribution of Listeria spp. (as a marker of contamination with L. monocytogenes) on slaughtered pig carcasses intended for the production of high-quality, Italian, dry-cured ham and examined the roles of the site sampled on the carcass, farming cycle (open versus closed), farm-to-slaughterhouse distance, and time spent in lairage. Samples were collected from swine carcasses (n = 150) before refrigeration, from three different carcass locations (head, shoulder, and thigh), and assessed for the presence of listeriae. A total of 115 carcasses were contaminated with Listeria spp. in at least one location. In all, 178 listeriae were isolated and identified: 130 Listeria innocua, 28 Listeria welshimeri, 17 Listeria ivanovii, and 3 L. monocytogenes. Listeriae were detected on 62.7% of heads, on 25.3% of shoulders, and on 30.7% of thighs, with significant differences between heads versus shoulders and thighs. Animals reared in closed-cycle farms were more contaminated (P < 0.05) than were animals from open-cycle farms (90 versus 71.8%). The distance between farms and slaughterhouse was not related to the contamination rate. Carcasses of swine that stayed in lairage before slaughtering for more than 10 h showed a higher degree of contamination (90%) and were positive for Listeria spp. in more sample sites (55%) compared with those held for less than 2 h (73% of carcasses and 33.3% of samples). Our results show that heads should be detached from carcasses immediately after slaughter for meat-safety purposes and the amount of time animals stay in lairage should be limited. These results will be useful for a more-valid implementation of good manufacturing processes for slaughtering.