Jakočiūnė, Džiuginta3; Pasquali, Frédérique4; da Silva, Cristiana Soares5; Löfström, Charlotta6; Hoorfar, Jeffrey1; Klein, Günter5; Manfreda, Gerardo4; Olsen, John Elmerdahl3
1 National Food Institute, Technical University of Denmark2 Division of Food Microbiology, National Food Institute, Technical University of Denmark3 University of Copenhagen4 University of Bologna5 University of Veterinary Medicine6 Research Group for Diagnostic Engineering, National Food Institute, Technical University of Denmark
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.
Applied and Environmental Microbiology, 2014, Vol 80, Issue 5, p. 1616-1622