FIG. 4.

Dose-dependent lysis of RBCs and HFFs by hemolysin-producing H. ducreyi. Symbols: ▵, 35000ΔAPC(pLS384-2) versus RBCs; ▴, 35000ΔAPC(pLS384-2) versus HFFs; ○, 35000ΔAPC(pLSBA+2) versus RBCs; ●, 35000ΔAPC(pLSBA+2) versus HFFs; □, 35000 versus RBCs; ■, 35000 versus HFFs. Dilutions of the strains indicated were made and incubated with washed horse RBCs or HFFs for 1 or 3 h, respectively. The percent lysis of RBCs and HFFs was determined as described in Materials and Methods. 35000ΔAPC(pLSSK) was not cytotoxic or hemolytic at any of the dilutions tested (data not shown). For each combination, the mean of a typical experiment is shown with standard errors. Hemolysis was measured in duplicate; LDH release was measured in triplicate. Three repetitions yielded similar results.