Cytotoxicity, Adhesion and Invasion ofClostridium septicumin Cultured Human Epithelial Cells (CACO-2, HEp-2): Pathological Significance of Swarm Cell DifferentiationCLINICAL MEDICINE/PATHOGENESIS

Clostridium septicumNCTC 282 was cytotoxic for CACO-2 and HEp-2 cells. However, HEp-2 cells were more resistant than CACO-2 cells toC. septicumcytotoxin. Short motile rod forms were considerably more cytotoxic than swarming bacteria. Bacterial adhesion only occurred with HEp-2, and short motile rod forms adhered in significantly greater numbers than swarming bacteria. Removal of bacterial flagella by mechanical shearing had little effect on adherence, demonstrating that these surface structures did not act as adhesins. Addition of a variety of monosaccharides (sucrose,D-fucose,L-fucose, mannose) to HEp-2 cell monolayers had little effect on bacterial adhesion, although maltose effected a 50% reduction. Invasion of HEp-2 cells byC. septicumoccurred with short motile rods, but not with swarming bacteria, suggesting that the initial stages of infection by this organism may be affected by the abilities of different cell forms to adhere to and invade epithelial cells. Since cytotoxicity, adherence and epithelial cell invasion byC. septicumis dependent on bacterial form, differentiation of the organism into swarm cells in response to environmental factors will influence the pathogenesis of infection.