A modified most probable number (MPN) assay to quantify Salmonella in raw and ready to cook chicken products

Authors: He, Yiping; Capobianco Jr, Joseph; Dykes, Gretchen; Armstrong, Cheryl; Chen, Chin Yi; Counihan, Katrina; Lee, Joseph; Reed, Sue; Tilman, Shannon

Submitted to: Journal of Visualized Experiments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/27/2025
Publication Date: 1/31/2025
Citation: He, Y., Capobianco Jr, J.A., Dykes, G.E., Armstrong, C.M., Chen, C., Counihan, K.L., Lee, J., Reed, S.A., Tilman, S.M. 2025. A modified most probable number (MPN) assay to quantify Salmonella in raw and ready to cook chicken products. Journal of Visualized Experiments. Article e67910. https://doi.org/10.3791/67910.
DOI: https://doi.org/10.3791/67910

Interpretive Summary: Salmonella contamination in poultry products is a major public health concern, causing illness and economic loss. Existing testing methods detect only the presence of Salmonella, without measuring the amount, which limits the ability to fully assess contamination risks. This study developed a new testing method that not only detects Salmonella but also quantifies it in ready-to-cook poultry products, like frozen chicken cordon bleu. By washing and concentrating samples and using advanced molecular techniques, this method provides more precise results, helping food producers identify even low levels of contamination. The study found that this new method is more sensitive than traditional approaches, particularly when detecting small amounts of bacteria. This improvement means food processors and regulatory agencies can better identify and address contamination risks, leading to safer poultry products and fewer foodborne illnesses. The new method is a valuable tool in the ongoing efforts to protect public health and enhance food safety standards.

Technical Abstract: Salmonella is a leading cause of foodborne illness in the United States, particularly in poultry products. Traditional methods for detecting Salmonella focus on prevalence rather than quantification, which limits their utility in assessing contamination levels and risks. This study introduces a novel most probable number (MPN) assay designed to quantify Salmonella in ready-to-cook poultry products, such as chicken cordon bleu. The method involves washing the poultry sample, concentrating the rinse through centrifugation, and serially diluting it in a 48-well block. The MPN assay is integrated with the LAMP method to provide a sensitive, accurate, and rapid quantification of Salmonella contamination within the same timeframe as existing FSIS protocols. Results show a strong linear correlation between the MPN-LAMP measurements and theoretical inoculation levels (R² = 0.933). However, variability at lower concentrations highlights challenges in accurately detecting Salmonella at these levels, with the practical lower limit of detection estimated at approximately 300 CFU/g. Potential refinements to improve the protocol’s applicability include increasing the quantity sampled to further improve the limit of detection, optimizing enrichment media formulations, and expanding molecular detection to target multiple Salmonella serovars. Overall, this study presents a practical tool for the food industry, enabling reliable quantification of Salmonella contamination in poultry products, contributing to improved food safety and public health.