Prevalence and characterization of Listeria monocytogenes in deboning and slicing areas of Spanish dry-cured ham processing

The Listeria monocytogenes diversity throughout deboning, compressing and slicing of Spanish dry-cured ham processing among and within 6 production plants after cleaning and disinfection in two different seasons (autumn/winter and spring/summer) was evaluated in this work. L. monocytogenes isolates (n = 66), collected from deboning area (72.7%) and compressing and slicing areas (27.3%), were serotyped as 1/2b (65.1%), 1/2a (27.3%), 1/2c (6.1%) and 4b (1.5%) by PCR-based methods. The typing of the 66 isolates of L. monocytogenes by PFGE using the ApaI and SgsI enzymes revealed a high diversity with 52 pulsotypes and showed cross-contamination within each plant. The frequency of isolation of L. monocytogenes was higher in spring/summer than in autumn/winter. Although L. monocytogenes was not detected in any of the analyzed dry-cured ham samples, the presence of some pulsotypes and cross-contamination in the different industries suppose a hazard of contamination by this pathogen during deboning and slicing of dry-cured ham. The use of molecular typing techniques, such as PCR-based methods and PFGE characterization, could be used to trace the sources, distribution and routes of L. monocytogenes contamination throughout deboning and slicing of dry-cured ham.