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 experi mentally infected hens. Salmonella enteritidis was isolated from the p reovulatory 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 attachmen t to hen ovarian granulosa cells and HEp-2 cells. Salmonella enteritid is demonstrated three different patterns of attachment to granulosa ce lls, namely, local, diffuse, and aggregative; whereas, only local atta chment pattern was observed on HEp-2 cells. The total number of S. ent eritidis isolates that demonstrated any pattern of attachment was sign ificantly 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 ma ture and developing follicles of the hen ovary. This suggests that S. enteritidis can colonize the preovulatory follicles at different stage s 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 bac teria to granulosa cells. These results suggest that S. enteritidis ca n colonize the preovulatory follicles by interacting with the ovarian granulosa cells and that adhesive proteins ma be involved in this proc ess.