Contribution of fimbriae and flagella of Salmonella enteritidis to colonization and invasion of chicks

Isogenic mutants of Salmonella enteritidis defective for the elaboration of fimbrial types SEF14, SEF17, SEF21 and flagella were used to study the con tribution these organelles made to colonization, invasion and lateral trans fer in young chicks. The caecum, liver and spleen were colonized within 24 h following oral inoculation of 1-day-old chicks with 10(5) wild-type S. en teritidis strain LA5. However, for some mutants, the numbers of organisms r ecovered from internal organs was reduced significantly, particularly at 24 h post-inoculum, which supported the hypothesis that the organelles contri bute to invasion and dissemination to internal organs. Specifically, mutati ons affecting SEF17, SEF21 and flagella contributed to a delay in colonizat ion of the spleen, and those affecting SEF21 and flagella delayed colonizat ion of the liver. Lower numbers of bacteria were recovered from the caecum with mutants deficient in elaboration of SEF21. Sentinel birds were coloniz ed by LA5 or EAV40 (14(-), 17(-), 21(-), fla(-)) directly from the environm ent within 2 days, although a consistent slight delay was observed with the multiple mutant. Overall, our data suggest a collective role for SEF17, SE F21 and flagella, but not SEF14, in the early stages of colonization and in vasion of young chicks by S. enteritidis, but these surface appendages appe ar unnecessary for colonization of birds from their immediate environment.