Cytotoxicity and reduction of animal cell growth by Clostridium M-55 spores and their extracts.

Abstract

Animal cells were incubated in the presence of Clostridium M-55 spores, extracts derived therefrom, or filtrates in test tubes and in Petri dishes. Cytotoxicity was determined either by the dye exclusion test or the adhesiveness efficiency, while the animal cells growth reduction was estimated either by the plating efficiency or the doubling time. Clostridium M-55 spores, mixed with animal cells in suspension, reduced the heteroploid malignant cell viability to 35% after 28 hours' contact. Increasing the multiplicity index of spores to animal cells resulted in a greater degree of cytotoxicity. Allowing the animal cells to sediment and stretch on the bottom of the Petri dishes showed that M-55 spores exerted a slight cytotoxic activity on the murine malignant cell lines while not significantly on the human malignant cell line and the simian cells prepared from normal animals. An important cell growth reduction was observed on all malignant cell lines as determined by plating efficiency. Increasing the multiplicity index of spores to animal cells did not lead to any significant further reduction in plating efficiency. Spore extracts were as effective as the spores themselves in reducing the heteroploid malignant cell growth. The M-55 culture filtrates were very active and reduced malignant cell growth as determined by their plating efficiency and their doubling time. Filtrates prepared from extracted vegetative forms of Clostridium M-55 bacilli were not active. Neither cytotoxicity nor cell growth reduction was observed in any way on diploid kidney cells derived from normal healthy monkeys.