Rapid detection of Salmonella Typhimurium in egg biofilms on three different surfaces using long-read sequencing

Authors: Bermudez-Aguirre, Luz; Tilman, Shannon; Niemira, Brendan; Counihan, Katrina; Uknalis, Joseph

Submitted to: Microorganisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/26/2025
Publication Date: 2/28/2025
Citation: Bermudez-Aguirre, L.D., Tilman, S.M., Niemira, B.A., Counihan, K.L., Uknalis, J. 2025. Rapid detection of Salmonella Typhimurium in egg biofilms on three different surfaces using long-read sequencing. Microorganisms. https://doi.org/10.3390/.
DOI: https://doi.org/10.3390/

Interpretive Summary: Salmonella is a bacterium that can be present in eggs and egg products and cause illness if eaten. Egg processing equipment is routinely cleaned to remove disease-causing organisms, but Salmonella can resist the killing effects of some cleaners and form biofilms. A biofilm consists of bacteria in a slime layer that is difficult to remove. This work studied the ability of Salmonella Typhimurium to form biofilms in liquid whole egg on three common food-contact surfaces, stainless steel, silicone, and nylon, during the first five hours of incubation and compare traditional methods to innovative and fast detection techniques. The results from traditional plating methods showed that Salmonella cells could be detected after 3 hours of incubation, and higher numbers of Salmonella attached to silicone than the other materials. The newer, faster method of long-read DNA sequencing detected Salmonella on all 3 surfaces after only 1 hour of incubation. The results of this study suggest that long-read sequencing could be very useful for detecting Salmonella at lower concentrations in the processing environment and faster than traditional methods. Earlier detection would allow the use of effective interventions to control and remove the Salmonella biofilms and protect human health.

Technical Abstract: Salmonella is a pathogenic microorganism linked to foodborne outbreaks associated with egg and egg products. This microorganism can resist sanitation of the egg processing equipment and form biofilms. The main challenge is detecting Salmonella cells in the early stages of biofilm formation to use effective interventions to control and remove the Salmonella biofilms. This work aimed to study the biofilm formation of S. Typhimurium in liquid whole egg (LWE) on three common food-contact surfaces, stainless steel, silicone, and nylon, during the first five hours of incubation at 37°C and compare traditional microbiological methods to innovative and fast detection techniques. The results showed that using general plate counts, Salmonella cells were detected after three h of incubation with less than 1 – log of growth, silicone was the material with most cells attached, followed by stainless steel. Long-read whole genome sequencing detected Salmonella on stainless steel, silicone, and nylon after only one h of incubation. The results of this study suggest that long-read sequencing could be very useful for detecting Salmonella at low concentrations in the processing environment.