Studies on the mechanism of transovarian transmission of Salmonella enteritidis in laying hens
Abstract
Food poisoning caused by Salmonella enteritidis following consumption of contaminated shell eggs is a major public health concern. Epidemiological and microbiological investigations indicated that in vivo contamination of the egg occurs in the reproductive tract of the laying hen. The present study was conducted to understand the contamination of yolk prior to ovulation. After oral inoculations of 140 laying hens with S. enteritidis, the organism was isolated from the preovulatory follicles in 16 birds (from follicle membrane alone in 10 birds, from the follicle yolk alone in four birds and from both membrane and yolk in two birds). This suggested that S. enteritidis interacted with cellular component(s) in the follicular wall. Chicken ovarian granulosa cells, a component of the follicular wall, were cultured in vitro and were used to demonstrate three different patterns of S. enteritidis attachment to these cells namely, local, diffuse, and aggregative. In addition, S. enteritidis can invade the granulosa cells in vitro and multiply in the cytoplasm. Preincubation of bacteria with the tetrapeptide arginine-glycine-aspartate-serine, the amino acid sequence known to mediate the interaction of adhesive glycoproteins with cells, inhibited in vitro attachment of bacteria to granulosa cells. Preincubation of granulosa cells with anti-chicken fibronectin serum or a purified 14 kilodalton fimbrial protein inhibited bacterial attachment to granulosa cells in vitro. Laying hens were orally inoculated with two strains of S. enteritidis with different fimbrial proteins (21 kilodalton and 14 kilodalton) and one strain without fimbriae. Decreased cecal colonization and fecal shedding of the organism were observed in hens that were inoculated with the strain that did not express surface fimbriae compared to birds inoculated with other two strains ($P < .05).$ Mean serum antibody titers of birds inoculated with this strain were also lower than titers of hens inoculated with the other two strains. Immunoblot of bacterial outer membrane structures revealed antibodies against major membrane associated proteins, 14 kilodalton fimbriae and lipopolysaccharide. Fimbrial proteins may mediate attachment of S. enteritidis to cecal epithelium and are able to elicit serum antibodies after oral inoculation.
Degree
Ph.D.
Advisors
Thaker, Purdue University.
Subject Area
Microbiology|Food science|Livestock
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