FIG. 3.

Hemolysin is cytotoxic to HFFs. H. ducreyi strains (ca. 5 × 10⁷ CFU) were incubated with HFFs (2 × 10⁴) for 3 h, and the LDH activity present in culture supernatants was measured. For each strain, the mean of a typical experiment performed in triplicate is shown with standard errors. The experiment was repeated at least three times with similar results.