MECHANISM OF TRANSOVARIAN TRANSMISSION OF SALMONELLA-ENTERITIDIS IN LAYING HENS

To understand the mechanism of transovarian transmission of Salmonella enteritidis in laying hens, experiments were conducted to examine the isolation of S. enteritidis from the preovulatory follicles of experimentally infected hens. Salmonella enteritidis was isolated from the preovulatory follicles in 16 birds (from follicle membrane alone in 10 birds, from the follicle yolk alone in 4 birds, and from both membrane and yolk in 2 birds). In addition, 83 S. enteritidis isolates of the major phage types prevalent in United States were tested for attachment to hen ovarian granulosa cells and HEp-2 cells. Salmonella enteritidis demonstrated three different patterns of attachment to granulosa cells, namely, local, diffuse, and aggregative; whereas, only local attachment pattern was observed on HEp-2 cells. The total number of S. enteritidis isolates that demonstrated any pattern of attachment was significantly greater on the granulosa cells than on HEp-2 cells (P < .05). Salmonella enteritidis isolates of phage Types 8 and 28 demonstrated similar patterns of attachment on granulosa cells derived from the mature and developing follicles of the hen ovary. This suggests that S. enteritidis can colonize the preovulatory follicles at different stages of development. Preincubation of bacteria with the tetrapeptide arg-gly-asp-ser, the amino acid sequence known to mediate the interaction of adhesive proteins with cells, abrogated the local attachment of bacteria to granulosa cells. These results suggest that S. enteritidis can colonize the preovulatory follicles by interacting with the ovarian granulosa cells and that adhesive proteins ma be involved in this process.