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Role of lipooligosaccharides in experimental dermal lesions caused by Haemophilus ducreyi
A A Campagnari1, L M Wild, G E Griffiths
1Department of Medicine, School of Medicine, State University of New York, Buffalo 14215.
Abstract:
The mouse and rabbit intradermal injection models have been used to define factors that may be important in Haemophilus ducreyi pathogenesis. We used H. ducreyi strains with diverse geographic origins and phenotypic characteristics to evaluate the experimental models. Injection of live and heat-killed bacteria caused skin abscesses in both models. Semiquantitative cultures of skin injected with live bacteria showed that H. ducreyi failed to replicate in animal tissue. These data suggested that the experimental lesions were caused by a heat-stable substance such as lipooligosaccharide (LOS). In mice, injection of H. ducreyi and Haemophilus influenzae LOS and Escherichia coli lipopolysaccharide caused mild to moderate inflammation. In rabbits, injection of H. ducreyi LOS caused intradermal abscesses that were histologically similar to those caused by live and heat-killed bacteria. H. ducreyi and Neisseria gonorrhoeae LOS caused significantly larger lesions than equivalent amounts of H. influenzae LOS and E. coli lipopolysaccharide in the rabbit model. We conclude that the intradermal injection models are not valid models to study the growth of H. ducreyi in vivo. However, these data indicate that H. ducreyi LOS may play an important role in the pathogenesis of chancroid and that the rabbit model should be useful in studying H. ducreyi LOS toxicity at the cellular level.
Insights
Haemophilus ducreyi lipooligosaccharide (LOS) causes skin abscesses in rabbits, suggesting its role in chancroid pathogenesis. However, mouse and rabbit models do not support H. ducreyi growth in vivo.
Area of Science:
- Microbiology
- Immunology
- Pathogenesis
Background:
- Intradermal injection models in mice and rabbits are used to study Haemophilus ducreyi pathogenesis.
- H. ducreyi strains from diverse origins and with varied characteristics were evaluated.
Purpose of the Study:
- To evaluate the validity of mouse and rabbit intradermal injection models for studying H. ducreyi pathogenesis.
- To investigate the role of H. ducreyi lipooligosaccharide (LOS) in experimental skin lesions.
Main Methods:
- Injection of live, heat-killed H. ducreyi, and purified LOS into mouse and rabbit skin.
- Histological examination and semiquantitative cultures of induced skin lesions.
- Comparison of lesion severity induced by H. ducreyi LOS with other bacterial endotoxins.
Main Results:
- Live and heat-killed H. ducreyi induced skin abscesses in both models, but bacteria did not replicate in tissue.
- H. ducreyi LOS induced intradermal abscesses in rabbits, similar to live/heat-killed bacteria.
- H. ducreyi LOS induced more severe lesions than LOS/LPS from H. influenzae and E. coli in rabbits.
Conclusions:
- Mouse and rabbit intradermal models are unsuitable for studying H. ducreyi replication in vivo.
- H. ducreyi LOS is a significant factor in chancroid pathogenesis.
- The rabbit model is valuable for studying H. ducreyi LOS toxicity at a cellular level.