Table 1.

The 50% Infectious Dose of Clostridium difficile Strain 630 and Mutant Spores in a Murine Model^a

Strain	50% Infectious Dose
CotE+	101
CotE–	103
CotEC–	102.3

^aMice are considered positive for Clostridium difficile infection when cecum tests positive for toxin and colony-forming units 2 logs higher than initial dose.