C. difficile toxin production ranges and statistics under different culture conditions from PM1–8.

aFor measurable toxin levels, the numbers indicate toxin concentrations in supernatants of C. difficile grown under different PM conditions.bThe P values were obtained from t-test on the dye reduction rates by CHO-k1 cells in the presence vs absence of C. difficile supernatants collected from different PM conditions.cBelow the measurable limit in CHO-k1 cell assay medium of 0.122 ng/ml. Note that the concentration of the toxin in the cell assay medium is 21-fold diluted from the bacterial supernatant (see Materials and Methods).