a b s t r a c tListeria monocytogenes is a foodborne bacterial pathogen of great concern to food industry. This is mainly due to its capacity to grow at low temperatures, its wide distribution in the environment and ability to adhere to various surfaces that come into contact with food. The aim of this study was to investigate the clonal relationship among L. monocytogenes isolates. Our purpose was to better understand the diversity of this pathogen in foods and food production chains in southern Rio Grande do Sul (Brazil). Forty four L. monocytogenes strains were characterized by serotyping and PFGE. Six different serotypes were found in the food and food environment (1/2a, 1/2b, 1/2c, 3a, 4b, 4e) and combination of macrorestriction patterns using AscI and ApaI, yielded 29 different pulsotypes. Strains with identical restriction patterns were isolated from foods of different sources and environments at different times. The presence of persistent strains of L. monocytogenes emphasizes the importance of cross-contamination in these food processing environments. It is likely that this occurs mainly due to ineffective cleaning and sanitization procedures, which allow for the survival and adaptation of these strains in the food processing environment, thereby causing persistence and contamination of final products.

No abstract

No abstract

Listeria monocytogenes is a bacterium capable to adhere to the surfaces of equipment and utensils and subsequently form biofilms. It can to persist in the food processing environmental for extended periods of time being able to contaminate the final product. The aim of this study was to trace the contamination route of L. monocytogenes on a fresh mixed sausage processing line, from raw material to the final product. The isolates obtained were characterized by serotyping and molecular typing by pulsed-field gel electrophoresis (PFGE) using the restriction enzymes ApaI and AscI. L. monocytogenes was detected in 25% of the samples. The samples of raw material were not contaminated, however, the microorganism was detected in 21% of the environmental samples (food contact and non-food contact), 20.8% of the equipments, 20% of the food worker's hands, 40% of the mass ready to packaging and in all the final products samples, demonstrating that the contamination of final product occurred during the processing and the importance of cross contamination. PFGE yielded 22 pulsotypes wich formed 7 clusters, and serotyping yielded 3 serotypes and 1 serogroup, however, the presence of serotypes 4b and 1/2b in the final product is of great concern for public health. The tracing of contamination showed that some strains are adapted and persisted in the processing environment in this industry.