Adhesion capacity and biofilm formation by Escherechia coli and Salmonella sp. on tomato (Solanum lycopersicum L.) during the postharvest stage

Tomato (Solanum lycopersicum L.) is one of the most cultivated and consumed vegetables in the world and has high economic value. Some pathogenic microorganisms such as Escherichia coli O157:H7 and Salmonella spp. can develop microbial aggregates in the form of biofilm in the fruits and they have been associated with multiple outbreaks of gastrointestinal illness. The objective of this study was to evaluate the adhesion capacity and biofilm formation of E. coli OND:H10, E. coli O157:H7 and Salmonella sp. on tomato fruits during the postharvest stage. A control was included. We measured the formation of biofilm during 13 consecutive days, including quantification of Log CFU mL^‑1 as well as physicochemical variables including fruit weight, color, juice pH, titratable acidity, and total soluble solids. There were significant differences among the 4 treatments and the 13 d elapsed. The average optical density (OD) for the treatments was as follows: E. coli OND:H10 (0.78 nm), E. coli O157:H7 (1.51 nm), Salmonella sp. (1.42 nm) and control, (1.47 nm), with better biofilm formation 4 and 5 d after inoculation (DAI). This is consistent with the higher CFU counts 4, 5 and 6 DAI, with a mean of 3.65 Log CFU mL^‑1, these results confirm that pathogens such as E. coli and Salmonella can adhere to the fruit, forming a biofilm that makes them a potential threat to food safety and source of infectious disease.