Adhesion of Salmonella enterica var Enteritidis strains lacking fimbriae and flagella to rat ileal explants cultured at the air interface or submerged in tissue culture medium

Rat ileal air interface and submerged explant models were developed and use d to compare the adhesion of Salmonella enterica var Enteritidis wild-type strains with that of their isogenic single and multiple deletion mutants. T he modified strains studied were defective for fimbriae, flagella, motility or chemotaxis and binding was assessed on tissues with and without an inta ct mucus layer. A multiple afimbriate/aflagellate (fim(-)/fla(-)) strain, a fimbriate but aflagellate (fla(-)) strain and a fimbriate/flagellate but n on-motile (mot(-)) strain bound significantly less extensively to the expla nts than the corresponding wild-type strains. With the submerged explant mo del this difference was evident in tissues with or without a mucus layer, w hereas in the air interface model it was observed only in tissues,vith an i ntact mucus layer. A smooth swimming chemotaxis-defective (che(-)) strain a nd single or multiple afimbriate strains bound to explants as well as their corresponding wild-type strain. This suggests that under the present exper imental conditions fimbriae were not essential for attachment of S. enteric a var Enteritidis to rat ileal explants, However; the possession of active flagella did appear to be an important factor. in enabling salmonellae to p enetrate the gastrointestinal mucus layer and attach specifically to epithe lial cells.