Biofilm formation on stainless steel by Staphylococcus epidermidis in milk and influence of glucose and sodium chloride on the development of ica-mediated biofilms

Staphylococcus epidermidis may form biofilms in milk processing plants and secondarily contaminate milk products. In this study, the ability of S. epidermidis to form a biofilm in milk and the influence of glucose and NaCl on biofilm formation were analysed. Biofilm production on stainless steel was investigated at 30 °C in pasteurized milk and in milk containing glucose, NaCl or both glucose and NaCl. Biofilm formation was evaluated by monitoring of colony-forming units (cfu) on stainless chips and by real-time quantitative PCR analysis of the icaA and σB transcripts. An increase in cfu and icaA transcription was observed after 20 h incubation, especially in milk containing glucose and NaCl. NaCl alone was shown to present a greater risk of biofilm development in milk than glucose alone, but the NaCl/glucose combination represented the highest risk. The σB factor did not seem to be involved in biofilm formation under the conditions of this study.