Infectious Diseases 2018

Infectious Diseases 2018

Genetic and phenotypic properties of SE isolates influence the multiplication and survival in eggs

Journal of Food Protection, Vol. 81, No. 6, 2018, Pages 876–880 19 May, 2018

Contamination of the edible interior contents of eggs by Salmonella enterica subsp. enterica serovar Enteritidis is an internationally significant public health concern. Internally contaminated eggs are produced as a consequence of Salmonella Enteritidis (SE) infection of the reproductive tissues of laying hens. However, this pathogen is found at a very low frequency in commercially produced eggs, and freshly laid eggs seldom harbor more than a few dozen bacterial cells. Accordingly, prompt refrigeration of eggs to prevent Salmonella multiplication to more dangerous levels during storage has been identified as an effective practice to reduce the risk of egg-transmitted illness. The efficacy of refrigeration for preventing the expansion of small SE populations depends on the interaction among the location of contamination within eggs, the capabilities of contaminant strains to survive or multiply, and the rate at which growth-restricting temperatures are attained.
A new study suggest that genetic and phenotypic properties of different SE isolates are involved. Differences observed among individual strains suggested that maintenance of the fimbrial gene sefD may have positive genetic selection value by improving fitness to grow inside egg yolk, whereas the antibiotic resistance gene blaTEM-1 tet(A) appeared to have negative genetic selection value by decreasing fitness to survive in egg albumen.