Enumeration of Salmonellae in Table Eggs, Pasteurized Egg Products, and Egg-Containing Dishes by Using Quantitative Real-Time PCR

Džiuginta Jakočiūnė, Frédérique Pasquali, Cristiana Soares da Silva, Charlotta Löfström, Jeffrey Hoorfar, Günter Klein, Gerardo Manfreda, John Elmerdahl Olsen

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Abstract

Salmonellae are a major cause of food-borne outbreaks in Europe, with eggs and egg products being identified as major sources. Due to the low levels of salmonellae in eggs and egg products, direct quantification is difficult. In the present study, enrichment quantitative real-time PCR (qPCR) was employed for enumeration of salmonellae in different matrices: table eggs, pasteurized egg products, and egg-containing dishes. Salmonella enterica serovar Enteritidis and S. enterica serovar Tennessee were used to artificially contaminate these matrices. The results showed a linear regression between the numbers of salmonellae and the quantification cycle (Cq) values for all matrices used, with the exception of pasteurized egg white. Standard curves were constructed by using both stationary-phase cells and heat-stressed cells, with similar results. Finally, this method was used to evaluate the fate of salmonellae in two egg-containing dishes, long egg and tiramisu, at abused refrigeration temperatures, and results indicated the growth of bacteria over a 1-week period. In conclusion, enrichment qPCR was shown to be reliable for enumeration of salmonellae in different egg products.
Original languageEnglish
JournalApplied and Environmental Microbiology
Volume80
Issue number5
Pages (from-to)1616-1622
ISSN0099-2240
DOIs
Publication statusPublished - 2014

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