Occurrence of Listeria species in ready to eat foods.

Over 8000 ready to eat foods were examined for the presence of Listeria species. Overall, 5% of foods were found to contain these organisms. Higher occurrence was found in some foods such as chicken (11%) and fish (14%). Most of the Listeria species isolated were L. monocytogenes (49%) and L. innocua (36%) with lower numbers of other species. No seasonal pattern in the recovery of L. monocytogenes was found. Unsatisfactory or potentially hazardous levels of L. monocytogenes were found in 14 products (< 0.2%), mostly cooked meats. Undercooked chicken products appeared to present the greatest risk for the duration of this survey. The small number of samples which were potentially hazardous suggests that the risk to consumers is not high, and this is confirmed by the absence of clinical cases in the region during the period of study.