Short communicationTracking Listeria monocytogenes contamination and virulence-associated characteristics in the ready-to-eat meat-based food products industry according to the hygiene level
Introduction
In ready-to-eat food (RTE) industry, hygiene procedures are crucial to prevent microbial contamination of the processing environment, especially by Listeria monocytogenes (Muhterem-Uyar et al., 2015). To verify and monitor control measures, food and food environment microbiological sampling is commonly used. Auditing also plays an important role in the food safety management systems (FSMS), and should be based on good hygiene and manufacturing practices (GHMP) and hazard analysis and critical control points (HACCP) principles (Fraqueza and Barreto, 2015). To have a more comprehensive insight of the FSMS performance, a conjoined diagnosis using microbiological data and audit results should be adopted (Luning et al., 2011).
Over the last years, ready-to-eat meat-based food products (RTEMP) are among the foods most commonly associated with L. monocytogenes (EFSA and ECDC, 2015). There are several ways by which RTEMP can be contaminated by L. monocytogenes, namely by post-listericidal treatment recontamination due to contact with processing equipment or surfaces, in operations such as slicing, cutting and weighing (Henriques and Fraqueza, 2015, Muhterem-Uyar et al., 2015).
Because of the importance of L. monocytogenes to human health and the notable diversity in the pathogenicity among its strains (Borucki et al., 2003), subtyping and virulence characterization are of upmost importance. The main objectives of this work were (i) to characterize the potential virulence of L. monocytogenes isolates by genotypic and phenotypic methods, (ii) to identify the likely sources of contamination of final products by using the PFGE typing method, (iii) to relate the isolates virulence-associated characteristics and genetic profile with the hygiene assessment level of the RTEMP industries and (iv) to investigate the audit requisites with the highest relation with the occurrence of L. monocytogenes serogroups most frequently associated with human disease.
Section snippets
Industries characterization
Ten industrial units producing RTEMP located in the central region of Portugal were assessed using a GHMP and HACCP questionnaire with 82 closed-ended questions (yes or no answer), structured in six sections: industrial typology, standard operating procedures (SOP), analytical control, personal hygiene, hygiene program and food-processing technology, as described in Henriques et al. (2014). Each audit included: a) an on-site visit for procedure verification; b) a documental assessment regarding
Audit data
All the studied industries produce RTEMP using pork, veal and/or poultry meat as raw materials and diverse manufacturing practices and hygio-sanitary conditions, as described by Henriques et al. (2014). The technological processing included cooking, fermenting, drying, smoking or baking. In 8 of the 10 industries the final product was cut, shredded or diced before packaging in aerobic or modified atmosphere. All the establishments were above 50% of conformity in the audit so no plant was
Conclusion
Genotyping of L. monocytogenes isolates from the RTEMP industry revealed a genetically diverse population with low resistance to commonly used antibiotics. Subtyping revealed that contamination of final products does not seem to be uniquely related with the sampled direct food contact surfaces.
Enhancement of the FSMS in those industries is also needed. Industries with a high hygienic audit classification revealed higher probability to present L. monocytogenes serogroups more commonly associated
Acknowledgments
The authors gratefully acknowledge the participating industries, Maria Helena Fernandes, Maria José Fernandes, Maria Paula Silva and CIISA-Project UID/CVT/00276/2013. This work was supported by Project “Portuguese traditional meat products: strategies to improve safety and quality” (PTDC/AGR-ALI/119075/2010), Project PRODER-PA No13017, MAMAOT-IFAP, I. P. and FCT PhD research grant SFRH/BD/70711/2010.
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