FIG. 1.

(A) Toxin titers of C. difficile culture supernatants measured by cytotoxicity against Vero cells. Log₁₀ reciprocal titer, the reciprocal of the log of the lowest dilution of C. difficile culture supernatant required for >90% cell rounding. (B) Concentration of tolevamer required to neutralize toxins. Diagonally hatched bars, BI/027 strains; white bars, other C. difficile strains, primarily from ATCC; checkered bars, strains expressing TcdB only (no TcdA); dotted bars, strains producing a large amount of binary toxins; black bar, purified TcdA; horizontally hatched bar, purified TcdB. Error bars are the standard deviations. All C. difficile culture supernatants were tested at least three times, except for strains 8864 and 43596, which were tested only twice.