Characterization of the AgfBA Fimbrial Operon Encoding Thin Aggregative Fimbriae of Salmonella Enteritidis

Abstract

Of the several fimbrial types produced by the human enteropathogen Salmonella enteritidis, the thin aggregative fimbriae, SEF17, are particularly interesting being highly immunogenic, aggregative, extremely stable, cell surface structures which are widely distributed among Salmonella serovars (Collinson et al., 1991; Doran et al., 1993). These fimbriae are composed of a 17,000 Da fimbrin, AgfA, and require treatment with 90% formic acid before depolymerization occurs (Collinson et al., 1991). Diarrheagenic Escherichia coli strains produce biochemically and serologically related, thin, aggregative fimbriae (Collinson et al., 1992) called curli which are composed of polymerized CsgA fimbrins (Arnqvist et al., 1994). An agfA-specific, oligonucleotide probe capable of distinguishing agfA from csgA forms the basis for a valuable, new, Salmonella-specific, diagnostic test (Doran et al., 1993). The role(s) of SEF17 in Salmonella pathogenesis remain(s) to be elucidated but purified SEF17 binds fibronectin in vitro suggesting a possible role in facilitating bacterial-tissue interactions (Collinson et al., 1993).