Adherence of Salmonella typhimurium to small-intestinal enterocytes of the rat.

The adherence of radiolabeled Salmonella typhimurium to freshly isolated enterocytes of rats was studied. The results established that type 1 fimbriated strains adhered in significantly higher numbers than did related nonfimbriated strains. Adherence was inhibited by D-mannose and methyl alpha-D-mannoside. Results of kinetic studies indicated that adherence was biphasic; the number of bacteria that adhered per enterocyte remained constant for approximately 20 min and then increased rapidly under the assay conditions. The second phase was associated with structural damage to the enterocytes. The addition of chloramphenicol did not prevent the initial attachment of bacteria to enterocytes but did prevent the second phase. Viable and nonviable bacterial cells adhered to enterocytes, but only viable bacteria were destructive. Freshly isolated enterocytes (trypan blue impermeable) and enterocytes stored overnight (trypan blue permeable) were infected by viable S. typhimurium in a similar manner, suggesting that metabolic activity of the host cell was of less consequence than metabolic activity of the bacterial cells. A model for the role of mannose-sensitive fimbriae as a virulence factor is proposed.