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Surface structures and adherence properties of diverse strains of Haemophilus influenzae biogroup aegyptius
J W St Geme1, J R Gilsdorf, S Falkow
1Department of Microbiology and Immunology, Stanford University, California 94305-5402.
Abstract:
Haemophilus influenzae biogroup aegyptius is an important cause of conjunctivitis and has recently been associated with Brazilian purpuric fever (BPF), a fulminant systemic disease of children. To gain insight into the bacterial factors involved in the pathogenesis of this disease, we investigated the surface structures and adherence properties of eight different strains of H. influenzae biogroup aegyptius, including both BPF and non-BPF isolates. All eight strains were able to express long peritrichous pili similar to those observed in H. influenzae. As in H. influenzae, piliation correlated with colony binding of human erythrocytes. However, two strains were capable of hemagglutination in the absence of pili; in these strains, hemagglutination was insensitive to protease treatment, suggesting a nonproteinaceous hemagglutinin. All strains possessed short, thin, surface fibers distinct from long pili and demonstrated efficient attachment to cultured human conjunctival cells. Attachment to conjunctival cells occurred independently of long pili or a capacity for hemagglutination.
Insights
Haemophilus influenzae biogroup aegyptius causes conjunctivitis and Brazilian purpuric fever (BPF). This study explored bacterial surface structures and adherence, finding pili and unique hemagglutinins contribute to disease pathogenesis.
Area of Science:
- Microbiology
- Pathogenesis
- Bacterial Virulence Factors
Background:
- Haemophilus influenzae biogroup aegyptius is a significant cause of conjunctivitis.
- This bacterium is also linked to Brazilian purpuric fever (BPF), a severe childhood illness.
Purpose of the Study:
- To investigate the surface structures and adherence properties of H. influenzae biogroup aegyptius.
- To understand the bacterial factors contributing to Brazilian purpuric fever pathogenesis.
Main Methods:
- Examined eight H. influenzae biogroup aegyptius strains (BPF and non-BPF isolates).
- Analyzed surface structures, including pili and surface fibers.
- Assessed hemagglutination and erythrocyte binding capabilities.
- Evaluated adherence to cultured human conjunctival cells.
Main Results:
- All strains expressed long peritrichous pili, similar to H. influenzae.
- Piliation correlated with human erythrocyte binding.
- Two strains showed pili-independent, protease-resistant hemagglutination, indicating a nonproteinaceous hemagglutinin.
- All strains possessed short surface fibers and efficiently attached to conjunctival cells, independent of pili or hemagglutination.
Conclusions:
- H. influenzae biogroup aegyptius possesses diverse surface structures contributing to its virulence.
- Pili and unique hemagglutinins are implicated in the pathogenesis of conjunctivitis and Brazilian purpuric fever.