Isolation of skin permeability factors from culture filtrates of Salmonella typhimurium.

Engerotoxins isolated from Vibrio cholerae and toxigenic Escherichia coli cause permeability alterations in rabbit skin. Firm induration and erythema are observed within 18 to 24 h, and visualization of the reaction may be enhanced by intravenous injection of Pontamine sky blue dye. Two skin permeability factors (PF) have been found in culture filtrates of Salmonella typhimurium. A rapid acting factor, produced optimally in brain heart infusion broth at 37 degrees C by numerous Salmonella species, has a critical bluing time of 1 h after completion of skin testing. This rapid PF is heat stable at 100 degrees C for at least 4 h and has no associated induration. The delayed factor is heat labile, being completly destroyed within 30 min at 75 degrees C and causes marked duration of the rabbit skin within 18 h that is indistinguishable from the permeability reactions of V. cholerae and E. coli enterotoxins. Induration produced by the delayed PF is observed only after chromatography of the culture filtrate on a Sephadex G-100 column. Thus, the effects of the delayed PF appear to be masked or blocked by an inhibitor-like substance present in crude culture filtrates. Both early and delayed factors are estimated to have a molecular weight of at least 90,000. It is postulated that one or both of these factors may participate in the pathogenesis of Salmonella infections.