Response of long-term acid stress to biofilm formation of meat-related Salmonella Enteritidis

Abstract

Salmonella commonly preferred to survive in the pattern of biofilm rather than planktonic cells in food processing environment, where various stress was widely encountered. In the present study, the response of biofilm formation of four-isolate cocktail of Salmonella Enteritidis on stainless steel surface to long-term acid stress was determined within a pH range of 5.0–7.2. The results showed that a short-term weak acid stress (pH 6.0 and 5.5) could enhance the attachment of S. Enteritidis, whereas short-term harsh stress significantly reduced cells attachment; Long-term weak and harsh stress obviously inhibited the biofilm formation of S. Enteritidis as compared with control group (pH 7.2), and the inhibition was significant depend on pH values, however, no difference was observed in planktonic cells numbers. Many small cell clusters rather than large cells aggregates were observed by fluorescence microscopy in harsh stress group, however, a classical process of biofilm formation and the complex three-dimensional structure formed by dense aggregates were found in control group. Consistent finding was also revealed by the observation of ATR-FTIR, which suggested that the harsh acid stress decreased the amount of various components formed in biofilm matrix, in particular of polysaccharides and proteins. Our finding suggested that long-term harsh acid stress could exert a great impact on biofilm formation of S. Enteritidis, and the obtained information was benefit for developing novel disinfection procedures in food processing industry.