Identification of Genes Associated with Survival ofSalmonella entericaSerovar Enteritidis in Chicken Egg Albumen

Abstract

Salmonella enterica consists of over 2,000 serovars that are major causes of morbidity and mortality associated with contaminated food. Despite similarities among serovars of Salmonella enterica, many demonstrate unique host specificities, epidemiological characteristics, and clinical manifestations. One of the unique epidemiological characteristics of the serovar Enteritidis is that it is the only bacterium routinely transmitted to humans through intact chicken eggs. Therefore, Salmonella enterica serovar Enteritidis must be able to persist inside chicken eggs to be transmitted to humans, and its survival in egg is important for its transmission to the human population. The ability of Salmonella enterica serovar Enteritidis to survive in and transmit through eggs may have contributed to its drastically increased prevalence in the 1980s and 1990s. In the present study, using transposon-mediated mutagenesis, we have identified genes important for the association of Salmonella enterica serovar Enteritidis with chicken eggs. Our results indicate that genes involved in cell wall structural and functional integrity, and nucleic acid and amino acid metabolism are important for Salmonella enterica serovar Enteritidis to persist in egg albumen. Two regions unique to Salmonella enterica serovar Enteritidis were also identified, one of which enhanced the survival of a Salmonella enterica serovar Typhimurium isolate in egg albumen. The implication of our results to the serovar specificity of Salmonella enterica is also explored in the present study.

Molecular insights into farm animal and zoonoticSalmonellainfections

“…Improved survival in albumen is a feature of S. Enteritidis strains compared with serovar Typhimurium (Clavijo et al 2006). Screening of transposon mutants of S. Enteritidis PT4 for survival in egg albumen identified 36 mutations that conferred sensitivity to albumen (Clavijo et al 2006).…”

“…Screening of transposon mutants of S. Enteritidis PT4 for survival in egg albumen identified 36 mutations that conferred sensitivity to albumen (Clavijo et al 2006). Thirty-two of these mutations were mapped, with half affecting cell envelope components (e.g.…”

“…Genes putatively involved in DNA modification or repair have also been implicated in survival in albumen. The nucleases YafD and XthA (Lu et al 2003) and the putative S. Enteritidis-specific endonuclease SEN4287 (Clavijo et al 2006) are required for survival of S. Enteritidis in albumen and can confer improved survival upon serovar Typhimurium by an unknown mechanism.…”

Identification by PCR signature-tagged mutagenesis of attenuated Salmonella Pullorum mutants and corresponding genes in a chicken embryo model

“…The genes affected were involved in invasion (uvrY::Tn5), cell division (ftsN::Tn5), metabolism (miaA::Tn5, yabF::Tn5, citC::Tn5, folA::Tn5, rfbG::Tn5, unknown::Tn5), and bacterial defence (wza::Tn5). The genes identified were different from those identified previously as being required for virulence in 2-day-old broiler chickens [6,14].…”

Salmonella in Shell Eggs: Mechanisms, Prevention and Detection

“…Ovortransferrin is considered a major antimicrobial ingredient of the egg whites because it chelates iron, which is a critical growth factor for microorganisms such as Salmonella [61][62][63]. Ovotransferrin and lysozyme are known to generate pores on the surface of gram-negative bacteria resulting in membrane permeabilization [64,65].…”