Penetration of Salmonella enteritidis and Salmonella heidelberg into egg yolks in an in vitro contamination model

Abstract

Eggs that harbor Salmonella in their edible contents pose a significant risk of transmitting disease to consumers. Although Salmonella deposition inside yolks does not usually occur at a high frequency in naturally contaminated eggs, bacterial penetration through the vitelline membrane could lead to rapid and extensive multiplication in the nutrient-rich yolk contents. The present study used an in vitro egg contamination model to assess the ability of Salmonella strains to penetrate the vitelline membrane and multiply inside yolks. An S. enteritidis strain and 2 Salmonella heidelberg strains, initially inoculated onto the outside of the vitelline membrane, were able to enter the yolk contents (at frequencies ranging from 10 to 25% of experimentally contaminated eggs) during 24 h of incubation at 30 degrees C. Variants of these parent strains, obtained by in vivo passage into eggs laid by infected hens, penetrated the yolk membrane at significantly higher frequencies. These results demonstrate that pathogens such as S. enteritidis and S. heidelberg can penetrate into and begin to multiply inside the yolks of contaminated eggs during the first day of storage at warm temperatures.

Population Dynamics of Salmonella enterica Serotypes in Commercial Egg and Poultry Production

“…S. Heidelberg supplanted S. Enteritidis as the predominant serovar from 1997 to 2006, and in 2007, S. Kentucky was the most commonly isolated serovar (43). Both S. Heidelberg and S. Enteritidis colonize the birds' reproductive tracts and enter the eggs (55,57,58). One of the factors that likely contributed to the decline of S. Enteritidis is that the NPIP has targeted these bacteria for eradication in eggs since 1989 and in meats since 1994 (115).…”

“…S. Heidelberg colonizes the reproductive tracts of layers and enters eggs through mechanisms similar to those of S. Enteritidis (55)(56)(57). S. Heidelberg can colonize the ovary and oviduct and penetrate and thrive inside the hen's egg (51,58,95). S. Typhimurium, S. Enteritidis, or S. Pullorum preferentially colonizes the reproductive organs (ovary and preovulatory follicles) of mature laying hens and causes higher mortality in chicks than S. Heidelberg or S. Kentucky (94, 105).…”

Effect of Combination of Chitosan Coating and Gamma Irradiation on the Foodborne Pathogen Reduction and Nutritional Properties of Chicken Egg

“…그러나 계란에 함유된 영양분은 미생물의 성장에 최적 조건을 가지고 있으므로 뜨거운 물과 염소를 이용하는 세척 과정 중 큐티클 층이 파괴된 계란은 미 세척란에 비하여 저장 성이 오히려 더 급속히 떨어지게 된다 (Gast et al, 2005). 현재 이를 보완하기 위해 dextrin, sodium alginate 등 코팅 처리와 같은 방법 등 (Farag et al, 1994;Hong et al, 2007) …”

“…계란은 난각, 난각막, 난백 및 난황 등으로 구성 되어 있고, 무균 상태로 형성되나, 외부로 산란되는 과정에 서 오염원에 노출되어 장외 세균인 Salmonella, Escherichia coli, Enterobacter, Klebsiella 등이 계란 껍질에 오염되는 것 으로 알려져 있다 (Hong et al, 2007;Kim et al, 2008). 장내 세균 중 Salmonella나 E. coli는 식중독을 일으키는 가장 일반 적인 식중독 원인균이고, 이러한 박테리아는 구토와 설사를 유발하며, 특히 노약자에게 위험하다 (Gast et al, 2005). …”

“…장내 세균 중 Salmonella나 E. coli는 식중독을 일으키는 가장 일반 적인 식중독 원인균이고, 이러한 박테리아는 구토와 설사를 유발하며, 특히 노약자에게 위험하다 (Gast et al, 2005).…”