PM substrates giving middle levels of toxin productions by C. difficile ATCC 9689.

aOD (750 nm) difference between C. difficile under certain PM substrate and the same substrate without C. difficile.bToxin concentrations in C. difficile supernatant collected from different PM conditions, which were calculated from the average dye reduction rate by the CHO-k1 cells according to the equations in Table 1.cThe P values were obtained from t-test on the dye reduction rates of CHO-k1 cells in the presence or absence of C. difficile supernatants collected from different PM conditions.