Evaluation of the microbial ecology present in a meat industry through surface-sensors (sch): influence of resident microbiota on listeria monocytogenes.

Despite all the efforts to eliminate the microorganisms present on the surfaces in food industries, certain microbial communities can persist forming the resident microbiota. In fact, multiple studies show the transfer capacity of microorganisms between food, surfaces, hands and utensils, among others, highlighting the relevant role of cross-contamination in foodborne diseases (Dantas et al., 2018; González-Rivas et al., 2018; Jensen et al., 2017; Ripolles-Avila et al., 2018a; Ripolles-Avila et al., 2018b). Generally, Enterobacteriaceae, Pseudomonas spp., Bacillus spp., Acinetobacter spp., Staphylococcus spp. and lactic acid bacteria dominate and reside on the surfaces of food facilities (Møretrø & Langsrud, 2017). These resident microorganisms can either inhibit the proliferation of pathogens or, on the contrary, enhance their establishment in mixed biofilms (Giaouris et al., 2015). Consequently, resident microbiota can have a significant effect on the probability of finding L. monocytogenes on food premises (Carpentier & Chassaing, 2004; Ripolles-Avila et al., 2019). For example, in the presence of a natural microbiota on wooden shelves, inoculated L. monocytogenes remained stable or even decreased to 2 log (CFU/cm2) after twelve days of incubation at 15°C under all conditions tested. However, L. monocytogenes increased to 4 log (CFU/cm2) when the resident biofilm was thermally inactivated, suggesting that the ecosystem residing in wooden shelves is able to control certain pathogens (Mariani et al., 2011). L. monocytogenes can also frequently be isolated after sanitation and still remains the most challenging microbial threat to many food industries, including the meat processing industry (Møretrø et al., 2013). L. monocytogenes persistence appears to be strongly linked to the manufacture of products and not to the sustained arrival of raw material. Ortiz et al. (2010) showed that some clones survived in a studied manufacturing area for three years. On the other hand, resident bacteria may play a role in the persistence and spread of antimicrobial resistance genes (Verraes et al., 2013). For these reasons, progress in the identification of established bacteria in food processing environments is essential. Few studies have characterized the resident species and their ecological interactions with foodborne pathogens such as L. monocytogenes. Overlapping with a macro quantitative study of the contamination load on the surfaces of a meat industry carried out by Ripolles-Avila et al. (2019), the objective of this study was to evaluate the resident microbiota on the industrial sufaces. The specific purpose was to identify the resident microorganisms (aerobic mesophilic bacteria, lactic acid bacteria and yeasts and molds) after the cleaning and disinfection processes by means of implementing SCH sensors. Another objective was to compare the existing species in the different areas that could have a positive or negative effect on the presence of L. monocytogenes. As a long-term aim, this study was conducted to investigate the presence of possible inhibitors or enhancers of this persistent foodborne pathogen in the industry's microbiota to reinforce the control strategies of L. monocytogenes and optimize cleaning and disinfection protocols.

Author(s): Carolina Ripolles-Avila

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