Presence ofListeria monocytogenesin Prepared Foods: Analysis of Influencing Factors

Abstract

Although food‐borne outbreaks of listeriosis are uncommon, they remain a major public health problem. We assessed the prevalence of Listeria monocytogenes in prepared foods and the influence of different factors (including type of food or presence of accompanying bacteria). Results showed that accompanying bacteria cause interference in the sensitivity of the detection method, being half Fraser the enrichment medium of choice. In 2760 samples, the global prevalence of L. monocytogenes was 1.4%. In ready‐to‐eat foods, the highest prevalence (23.3%) was found in products containing fermented or cured ingredients and the prevalence was also higher in foods with high counts of aerobic bacteria and lactose‐positive Enterobacteriaceae, two indicators of process hygiene. We also found that foods stored in <0C had a higher prevalence (4.1%) of L. monocytogenes. In prepared foods, factors favoring the presence of L. monocytogenes could be some components of ready‐to‐eat foods, temperatures <0C, and presence of accompanying bacteria. Practical Applications Results are of relevance for practical application as this study was performed in the context of the routine practice of a food control company, with samples collected in different restoration centers from Spain. Results obtained have allowed identifying some factors favoring the presence of L. monocytogenes, which should be taken into account in the current practice of the manufacturing centers of prepared foods to avoid contamination by this bacterium. Based on our results, actions aimed at avoiding high numbers of accompanying bacteria as aerobic mesophilic bacteria (AMB) or Enterobacteriaceae should be taken into account. Special care should also be taken in the manufacturing of foods containing fermented or cured ingredients, as cheese. Finally, the manufacturing centers should also consider the risk of Listeria contamination due to the use of sophisticated machinery or due to the storage of prepared foods at temperatures <0C.

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“…L . monocytogenes is particularly problematic, as it can survive for long periods of time in a food processing environment and causes human listeriosis (Ben Braïek et al., 2019; Benito et al., 2017). The infection is mainly linked to the consumption of contaminated ready‐to‐eat foods, such as cheese and other dairy products, processed meats, salads, seafood, and raw eggs (Szymczak, Szymczak, & Trafiałek, 2020).…”