Effects of nutritional and environmental conditions on Salmonella sp. biofilm formation

Biofilm formation on food industry surfaces has important health and economic consequences, since they can serve as a potential source of contamination for food products, which may lead to food spoilage or transmission of diseases. Salmonella sp. is one of the most important foodborne pathogens and several studies have led to the discovery that these bacteria are capable of adhering and forming biofilms on different surfaces. The attachment of bacterial cells is affected by several factors, including the medium in which they are grown, motility, growth phase of the cells, type and properties of the inert material, presence of organic material, temperature, pH, contact time, and so on. This investigation focused on the study and quantification of the effects of temperature (20 to 40 °C), pH (4.5 to 7.5), and medium composition (0.5 to 2.5 g/L of peptone) on biofilm formation by Salmonella sp. on stainless steel through surface response modeling. Results highlighted that the target strain was able to adhere on stainless steel, under all the conditions tested. To assess potential differences, the aptitude to biofilm formation (ABF), defined as the time necessary to start adhesion on the surface, was calculated by using the Gompertz equation. This parameter was modeled through a stepwise regression procedure and experimental conditions resulting in the greater ABF were growth in poor media (1.0 to 1.5 g/L of peptone), incubation temperature of about 30 °C, pH close to 6.0. Practical Application: The importance of this work lies in its extension of our knowledge about the effect of different environmental conditions on Salmonella adherence to stainless steel food-processing equipment, as a better understanding of biofilms may provide valuable pathways for the prevention of biofilm formation.