Effect of sous-vide processing of fish on the virulence and antibiotic resistance of Listeria monocytogenes

Sous-vide is a cooking technique which is considered safe for food preparation, however, the recommended temperatures and times for preparing seafood and fish may not be sufficient to ensure safety, and additionally, thermal stress may cause changes in virulence and resistance. The objective of the present investigation was to determine the reduction of Listeria monocytogenes isolated from fish after sous-vide preparation. For this purpose flow cytometry was used. The impact of stress during the preparation of the fish-based dish using the sous-vide technique on the virulence potential and resistance profile was determined geno- and phenotypically. The study was conducted at four different temperatures, that are typical for fish preparation (42, 52, 57 and 60 °C) showing that none of them could be effective against L. monocytogenes. In addition, the investigation of changes in the virulence, phenotypic antibiotic resistance and gene expression showed that the stress during the preparation of sous-vide decrease virulence potential of the L. monocytogenes strains. It was observed that the greatest changes in antibiotic resistance profile were noted for tetracycline and notable changes were also observed for some strains in the case of fosfomycin and ciprofloxacin. Therefore it is important not to consider the sous-vide method as ensuring the microbiological quality of products, especially those with high contamination levels, and choose products of the best quality for processing.