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United States Department of Agriculture

Agricultural Research Service

Title: Rapid real-time PCR assays for detecting Salmonella in raw and ready-to-eat meats

Authors
item Patel, Jitu
item Bhagwat, Arvind

Submitted to: Acta Veterinaria
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 14, 2008
Publication Date: October 1, 2008
Citation: Patel, J.R., Bhagwat, A.A. 2008. Rapid real-time PCR assays for detecting Salmonella in raw and ready-to-eat meats. Acta Veterinaria Hungarica 56(4):451-458.

Interpretive Summary: Salmonella is one of the most frequent foodborne bacteria responsible for more than 1 million outbreaks and 500+ deaths every year in the United States. The detection of Salmonella is still primarily based on traditional culture methods recommended by the regulatory agencies that take several days to complete. A number of rapid alternative methods for detection of Salmonella from foods has been developed, including immunological and polymerase chain reaction (PCR) methods. Molecular Beacon probes and TaqMan probes are commonly used in PCR chemistry for the real-time detection of target bacteria. We optimized a molecular beacon real-time PCR assay for rapid (10-h) detection of Salmonella in meats. Raw (chicken, pork) and ready-to-eat (RTE) meats were artificially contaminated with Salmonella enterica serovar Typhimurium at the estimated level of 2 to 4 cells per 25 g. After 8 h of pre-enrichment in buffered peptone water, molecular beacon-based PCR assay was performed to detect contamination in raw and RTE meats. Comparative evaluation of USDA procedure with rapid PCR assay for meat samples (n=63) revealed 1 false negative pork sample with PCR assay. All uninoculated controls (n=34) but one sample were negative by both, 10-h PCR assay and USDA procedure. Developing rapid pathogen detection methods with shorter pre-enrichment times (8-h) and real-time data monitoring capabilities will benefit the industry in preventing recall of contaminated meats by stopping the contaminated products from being introduced into the marketplace.

Technical Abstract: A real-time PCR assay based on molecular beacon technologies was evaluated for the rapid detection of Salmonella in meats following 8h enrichment. Raw (chicken, pork) and ready-to-eat (RTE) meats were artificially contaminated with Salmonella enterica serovar Typhimurium at the estimated level of 2 to 4 cells per 25 g. After 8 h of pre-enrichment in buffered peptone water, molecular beacon-based PCR assay was performed to detect contamination in raw and RTE meats. The sensitivity and accuracy of the assay were compared with the conventional USDA microbiological procedure. Comparative evaluation of USDA procedure with rapid PCR assay for meat samples (n=63) revealed 1 false negative pork sample with PCR assay. All uninoculated controls (n=34) but one sample were negative by both, 10-h PCR assay and USDA procedure. Developing rapid pathogen detection methods with shorter pre-enrichment times (8-h) and real-time data monitoring capabilities will benefit the industry in preventing recall of contaminated meats by stopping the contaminated products from being introduced into the marketplace.

Last Modified: 7/28/2014