Sensitivity of smooth Salmonella cholerae-suis var kunzendorf field strains to antibody complement under various conditions.

Seventy-two field strains of smooth Salmonella cholerae-suis var kunzendorf were obtained from outbreaks of swine parathyroid. The field strains were examined for susceptibility to killing by antibody-complement (Ab-C) after they were exposed to Tris-EDTA, lysozyme, or saline solution. Considerable differences were found in susceptibility to killing by Ab-C in the strain population. Some strains were highly sensitive to Ab-C under all experimental conditions, whereas others became sensitive only after prior exposure to Tris-EDTA or to lysozyme. One strain was resistant to all treatments. Numerical decrease of colony-forming units by Tris-EDTA affected the population independently of decrease of the colony-forming units by Ab-C in saline solution. Evidence was obtained to indicate that Tris-EDTA may inhibit growth of S cholerae-suis in addition to the documented effect of Tris-EDTA on the release of lipopolysaccharide from the cell wall of gram-negative bacteria.