Cumulative experience with Haemophilus ducreyi 35000 in the human model ofexperimental infection

Background and Objectives: To study Haemophilus ducreyi pathogenesis, the a uthors developed an experimental model of infection in human volunteers. Th e authors analyze their cumulative experience with strain 35000 in the mode l and calculate the papule and pustule formation rates for estimated delive red doses (EDDs) ranging from 1 cfu to 100 cfu. Study Design: Sixty-five volunteers were included in the analysis. A total of 139 sites were available for calculation of the papule formation rate, a nd 117 sites were available for calculation of the pustule formation rates. Results: The effect of EDDs and probabilities of papule formation and the p ustule formation were dose-dependent. Increasing the EDD resulted in a high er probability of papule and pustule formation. Conclusion: H ducreyi is highly infectious for humans. Inoculation of an ED D of 1 cfu causes a papule formation rate of 50%. Pustule formation rates a re approximately 50% for 27 cfu and 90% for 100 cfu.