EFFECT OF PLANT ALKALOIDS ON THE SPORULATION OF A FOOD-BORNE PATHOGEN

Caffeine, theophylline and theobromine are structurally related plant alkaloids which are consumed in large amounts worldwide in the public diet. Clostridium perfringens, a foodborne pathogen, exerts its toxic effect on humans when producing a toxin during sporulation in the intestine. Investigations were undertaken to determine the effect these plant alkaloids have on the sporulation of the pathogen and subsequent toxin formation.

In the presence of 100 μg of caffeine per ml or 200 μg of theobromine per ml, sporulation of Clostridium perfringens NCTC 8679 rose from less than 1 to 80 or 85%. Enterotoxin concentration increased from undetectable levels to 450 μg/mg of cell extract protein. Heat-resistant spore levels increased from less than 1000 to between 1 x 10⁷ and 2 x 10⁷/ml. These effects were partially reversible by the addition of adenosine or thymidine. In the case of NCTC 8238, caffeine and theobromine caused a three- to fourfold increase in the percentages of cells possessing retractile spores and a similar increase in enterotoxin concentration. Heat-resistant spore levels, however, were unaffected. Inosine was ineffective in promoting sporulation in NCTC 8679. The mechanism by which caffeine stimulates sporulation of Clostridium perfringens was investigated. Results indicated that cultures exposed to caffeine had significantly elevated levels of intracellular adenosine and guanosine triphosphates.