Fimbriae- and flagella-mediated association with and invasion of cultured epithelial cells by Salmonella enteritidis

Salmonella enteritidis expresses flagella and several finely regulated fimb riae, including SEF14, SEF17 and SEF21 (type 1). A panel of mutants was pre pared in three strains of S. enteritidis to elucidate the role of these sur face appendages in the association with and invasion of cultured epithelial cells. In all assays, the naturally occurring regulatory-defective strain 27655R associated with tissue culture cells significantly more than wild-ty pe progenitor strains LA5 and S1400/94. Compared with wild-type strains, SE F14 mutants had no effect on association and invasion, whereas SEF17, SEF21 and aflagellate mutants showed significant reductions in both processes. H istological examination suggested a role for SEF17 in localized, aggregativ e adherence, which could be specifically blocked by anti-SEF17 sera and pur ified SEF17 fimbriae. SEF21-mediated association was neutralized by mannose and a specific monoclonal antibody, although to observe enhanced associati on it was necessary for the bacteria to be in fimbriate phase prior to infe ction. Additionally, aflagellate mutants associated and invaded less than m otile bacteria. This study demonstrated the potential for multifactorial as sociation and invasion of epithelial cells which involved SEF17 and SEF21 f imbriae, and flagella-mediated motility.