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, 199 (11), 1671-9

Experimental Infection of Human Volunteers With Haemophilus Ducreyi: Fifteen Years of Clinical Data and Experience

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Experimental Infection of Human Volunteers With Haemophilus Ducreyi: Fifteen Years of Clinical Data and Experience

Diane M Janowicz et al. J Infect Dis.

Abstract

Haemophilus ducreyi causes chancroid, which facilitates transmission of human immunodeficiency virus type 1. To better understand the biology of H. ducreyi, we developed a human inoculation model. In the present article, we describe clinical outcomes for 267 volunteers who were infected with H. ducreyi. There was a relationship between papule formation and estimated delivered dose. The outcome (either pustule formation or resolution) of infected sites for a given subject was not independent; the most important determinants of pustule formation were sex and host effects. When 41 subjects were infected a second time, their outcomes segregated toward their initial outcome, confirming the host effect. Subjects with pustules developed local symptoms that required withdrawal from the study after a mean of 8.6 days. There were 191 volunteers who had tissue biopsy performed, 173 of whom were available for follow-up analysis; 28 (16.2%) of these developed hypertrophic scars, but the model was otherwise safe. Mutant-parent trials confirmed key features in H. ducreyi pathogenesis, and the model has provided an opportunity to study differential human susceptibility to a bacterial infection.

Figures

Figure 1
Figure 1
Outcomes of volunteers who were infected at three sites with 35000HP and developed 0, 1, 2 or 3 pustules.
Figure 2
Figure 2
The relationship of estimated delivered dose and overall probabilities (with 95% CI) of papule (open circles) and pustule (+) formation, as predicted by logistic regression.
Figure 3
Figure 3
Papule formation rates for females (circle) and males (triangle) and pustule formation rates for females (+) and males (×) related to estimated delivered doses as predicted by logistic regression. For simplicity, the 95% CI are not shown.
Figure 4
Figure 4
The likelihood of forming a pustule on the second infection for volunteers who formed pustules (+) or who resolved (×) during their first infections.

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