Impact of temperature during the storage of table eggs on the viability of Salmonella

Salmonellosis is a foodborne infection of major economic importance. Contamination of table eggs with Salmonella, especially Salmonella enterica serovar Enteritidis, is a major health concern worldwide. Recently, S. enterica serovar Virchow has emerged as a major pathogen in Israel, where it is among the 3 most prevalent serovars found in poultry and the second most prevalent serovar isolated from individuals with salmonellosis. Although there is ample knowledge regarding the role of S. enterica serovar Enteritidis in contamination of eggs, virtually nothing is known regarding the possible association of S. enterica serovar Virchow with table eggs. Therefore, the scientists at Kimron Veterinary Institute, Dagan, Israel examined the capability of serovar Virchow to contaminate chicken eggs. Commercial table eggs were inoculated independently with serovar Enteritidis and with serovar Virchow cells at a concentration of 10(5) cfu/egg, either on the shell surface or by injection into the yolk. The numbers of live Salmonella cells on the shell and within the egg were determined at various time points. At both low (6oC) and room temperatures (25oC), S. enterica serovar Virchow was not detected on the eggshell after 2 weeks, whereas S. enterica serovar Enteritidis could be detected only sporadically at 25oC. In contrast, within the eggs, S. enterica serovar Virchow survived for up to 6 weeks at 6oC, and it multiplied up to 10(9) cfu/ml of egg content from 2 to 8 weeks postinoculation at 25oC. In comparison, S. enterica serovar Enteritidis survived within the eggs up to 8 weeks at 6oC and at 25oC. These results suggest that in cold storage, serovar Virchow is able to persist for long periods (6 weeks), and at room temperature, these bacteria can multiply within eggs and reach high concentrations. Therefore, eggs might be considered potential vectors for transmitting S. enterica serovar Virchow into the food chain [Lublin A and Sela S, The impact of temperature during the storage of table eggs on the viability of Salmonella enterica serovars Enteritidis and Virchow in the Eggs, Poult Sci, 2008, 87(11), 2208-2214]. Impact of temperature during the storage of table eggs on the viability of Salmonella