With the increased demand for lightly preserved and/or ready-to-eat (RTE) food products, the prevalence of the foodborne pathogen Listeria monocytogenes has increased, which is a public health concern.
A review published in Comprehensive Reviews in Food Science and Food Safety discusses the incidence, epidemiological importance, and contamination routes of L. monocytogenes in various aquatic ecosystems, seafood products, and processing environments. In addition, it summarizes the data obtained since the 1990s.
Listeria monocytogenes primarily enters the food production chain by cross-contamination in production plants, making this pathogen a major threat to the seafood industry. This pathogen generally contaminates food products at low or moderate levels, but the levels involved in listeriosis outbreaks are significantly higher. The majority of isolates from aquatic products belong to serotype 1/2a, and outbreaks have been linked to highly similar or even indistinguishable strains. Several seafood-processing plants are colonized by specific “in-house” flora containing special DNA subtypes of L. monocytogenes. In such cases, L. monocytogenes populations can persist and/or multiply despite the inherent obstacles to their growth in food preservation and manufacturing operations.
To reduce and prevent contamination in the processing environment and products, the authors highlight the need to detect the main sources of contamination and to understand the mechanisms underlying the persistence of differentL. monocytogenes strains in the environment. The key areas where Listeria spp. have been detected or where greatest Listeria contamination has been observed in the processing environment can be identified. In particular, drains and difficult-to-clean skinning areas as well as brine injection and slicing equipment are frequent reservoirs of persistent L. monocytogenes colonization in fish-processing plants; however, further research is required to confirm the original source of contamination.
The authors conclude that while cleaning and disinfection of the production plant should lower the prevalence of L. monocytogenes, there is an urgent need to design sanitation strategies that precisely target persistent strains, for example, using sanitizers with active ingredients more suitable for biofilms.