An isogenic haemolysin‐deficient mutant ofHaemophilus ducreyilacks the ability to produce cytopathic effects on human foreskin fibroblasts

摘要

The haemolysin ofHaemophilus ducreyiis the newest member of theProteus/Serratiafamily of pore‐forming toxins. In order to assess the role of the haemolysin in virulence, we constructed an isogenic haemolysin‐deficient mutant ofH. ducreyistrain 35000. This strain, designated 35000‐3, lacks detectable haemolytic activity. We testedH. ducreyistrains 35000 and 35000‐3 for their cytopathic activity against human foreskin fibroblasts (HFFs). We observed strong cytopathic activity when strain 35000 was co‐cultured with HFFs. In contrast, cytopathic activity was not observed when strain 35000‐3 was co‐cultured with HFF cells. We also analysed the isogenic pair ofH. ducreyistrains for cytopathic activity against HeLa cells and the keratinocyte cell line HaCaT. Strains 35000 and 35000‐3 were strongly cytotoxic when co‐cultured with HeLa cells. HaCaT monolayers were slightly damaged by cocultivation with strain 35000‐3 but this damage was much less than that observed when HaCaT cells were cocultured with strain 35000. These results indicate that theH. ducreyihaemolysin is responsible for the previously observed cytotoxic activity against HFF cells and is partially responsible for the activity observed with HaCaT cells. The haemolysin, however, is not responsible for the activity obser