Rapid estimation of Salmonella enterica contamination level in ground beef – Application of the time-to-positivity method using a combination of molecular detection and direct plating

Authors

Dayna M. Harhay, USDA ARS Roman L. Hruska U.S. Meat Animal Research CenterFollow
Margaret D. Weinroth, USDA ARS Roman L. Hruska U.S. Meat Animal Research Center
James L. Bono, USDA ARS Roman L. Hruska U.S. Meat Animal Research Center
Gregory P. Harhay, USDA ARS Roman L. Hruska U.S. Meat Animal Research CenterFollow
Joseph M. Bosilevac, USDA ARS Roman L. Hruska U.S. Meat Animal Research Center

Date of this Version

2-1-2021

Document Type

Article

Citation

https://doi.org/10.1016/j.fm.2020.103615

Food Microbiology, Volume 93, February 2021, 103615

Comments

U.S. government work

Abstract

Little progress has been made in decreasing the incidence rate of salmonellosis in the US over the past decade. Mitigating the contribution of contaminated raw meat to the salmonellosis incidence rate requires rapid methods for quantifying Salmonella, so that highly contaminated products can be removed before entering the food chain. Here we evaluated the use of Time-to-Positivity (TTP) as a rapid, semi-quantitative approach for estimating Salmonella contamination levels in ground beef. Growth rates of 14 Salmonella strains (inoculated at log 1 to −2 CFU/g) were characterized in lean ground beef mTSB enrichments and time-to-detection was determined using culture and molecular detection methods. Enrichments were sampled at five timepoints and results were used to construct a prediction model of estimated contamination level by TTP (superscript indicates time in hours) defined as TTP4: ≥5 CFU/g; TTP6: ≤5, ≥1 CFU/g; TTP8: ≤1, ≥0.01 CFU/g; with samples negative at 8 h estimated ≤0.01 CFU/g. Model performance measures showed high sensitivity (100%) and specificity (83% and 93% for two detection methods) for samples with a TTP4, with false negative rates of 0%.