In addition to the targeted and routine sampling that was performed
over the 23-month period, ingredient materials entering
the production facility were studied, to determine the prevalence of
Listeria species, and assess their significance as a potential transfer
route for contamination entering the facility. In total 77 ingredients
were assessed microbiologically using the ISO detection method for
Listeria species (Table 1). This comprised 46 poultry meat ingredients,
and 31 dry ingredients (normally used to flavor meat
products prior to cooking, and included starches and/or seasonings).
Some 31 of the 46 meat samples (67%) was positive for least 1
Listeria species. Of the 46 meat samples, 19 were positive for L.
monocytogenes, 16 were positive for Listeria welshimeri, and a
further 7 for Listeria innocua. Only 1 of the 31 dry ingredients was
positive for Listeria species, with a wheat flour sample containing L.
welshimeri.