Enhanced Fermentation of Mannitol and Release of Cytotoxin by Clostridium difficile in Alkaline Culture Media

Michael T. Kazamias
Jay F. Sperry, University of Rhode Island

Abstract

Clostridium difficile ATCC 43255 fermented less than 10% of the mannitol in a medium at pH 7; however, when the initial pH of the medium was adjusted to 8.5 or 9, about 80% of the mannitol was fermented. Cell extracts of C. difficile phosphorylated mannitol with phosphoenolpyruvate, not ATP, indicating a phosphoenolpyruvate phosphotransferase system transport phosphorylation of mannitol. The phosphorylation product was dehydrogenated by D-mannitol-1-phosphate:NAD oxidoreductase. Growth at an initial pH of 8.5 yielded cytotoxin titers of 10⁷ to 10⁸ in Trypticase-yeast extract-mannitol medium, with a titer of 10⁸ as early as 13 h.