Temperature and surface material can promote Pseudomonas fragi and Pseudomonas psychrophila biofilm production, with protection under refrigeration conditions of growth and persistence of Escherichia coli in fish meat.

Pseudomonas are part of the indigenous microbiota of different foods, where they gradually cause spoilage. In fish meat, Pseudomonas fragi and Pseudomonas psychrophila have been identified as important spoilers. The initial aim of this study was to investigate the physiological characteristics, adhesion and biofilm of P. fragi and P. psychrophila under temperatures related to the fish processing industry. The further aim was to define the problem of increased growth of pathogenic bacteria in the presence of spoilage bacteria in-vitro and in fish meat.Temperature dependence on physiological characteristics, adhesion and biofilm was observed. Hydrophobicity and autoaggregation were most prominent at 15 °C, and at this temperature also floating biofilm was formed. The adhesion of these Pseudomonas was up to 2 log CFU cm more pronounced on stainless steel than polystyrene, with up to 5-times greater biofilm biomass production at 5 °C on polystyrene. Furthermore, this paralleled at least 0.5 log CFU g increase of pathogenic bacterium Escherichia coli in fish meat.P. fragi and P. psychrophila adhesion and biofilm depends on the temperature, and is stimulated by temperatures that can occur during processing and storage of fish meat. Strong Pseudomonas biofilm formation under refrigeration conditions is protective for E. coli, potentially through providing more favourable conditions by ensuring higher concentration of nutrients. The interactions between spoilage Pseudomonas and pathogenic bacteria can occur through different mechanisms, and understanding of these is of particular importance to assure the overall quality and safety of fish meat and other proteinaceous foods. This article is protected by copyright. All rights reserved.