Fate and biofilm formation of Salmonella enterica subsp. enterica serovar Thompson on fresh strawberries stored under refrigeration and room temperatures

Abstract

Fresh strawberry is a popular, frequently fruit consumed, which is largely appreciated for its organoleptic characteristics and health benefits. However, different outbreaks caused by food-borne pathogens have been attributed to strawberry consumption. The persistence of bacteria on fruits like strawberries could be related to their ability to adhere and form biofilms on the surface. The present study aimed to evaluate the fate and biofilm formation capacity of Salmonella enterica subsp. enterica serovar Thompson in post-harvest strawberries stored at 4 and 7 °C for 192 h and 20 °C for 72 h. Fresh strawberries were spot inoculated to achieve an initial concentration of around 5 log CFU/g of S. Thompson. During storage at 20 °C, a 2-log reduction per gram was observed. At 7 and 4 °C, the S. Thompson population decreased to 1.7 and 2.0 log, respectively after 192 h of storage. A more marked decrease of the pathogen was observed at 4 °C, in comparison with a slight decay at 7 or 20 °C. On the other hand, the observations with scanning electron microscopy and confocal laser scanning microscopy demonstrated the formation of biofilm on the epidermis of the strawberry stored at all temperatures. This could be considered a mechanism adopted by the bacteria against stress during storage. Prevention of biofilm formation and disruption of biofilm in strawberries become essential for food safety.