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A virulent nonencapsulated Haemophilus influenzae
V Nizet1, K F Colina, J R Almquist
1Division of Infectious Disease, Children's Hospital and Medical Center, Seattle, WA 98105, USA.
The Journal of Infectious Diseases
|January 1, 1996
Summary
Nontypeable Haemophilus influenzae (NT-Hi) strain INT1 caused meningitis despite lacking capsule genes. DNA from this strain transferred invasive traits, suggesting novel virulence factors in this common pathogen.
Area of Science:
- Microbiology
- Infectious Diseases
- Genetics
Background:
- Nontypeable Haemophilus influenzae (NT-Hi) is a common cause of otitis media but rarely invasive disease.
- Capsular polysaccharide is a primary virulence factor for invasive Haemophilus influenzae.
Observation:
- A case of meningitis in a child was linked to NT-Hi strain INT1.
- Strain INT1 lacked detectable capsular polysaccharide production and the intact capsulation (cap) gene locus.
- INT1 successfully caused bacteremia and meningitis in rat models.
Findings:
- Genetic transformation experiments demonstrated that DNA from INT1 conferred an invasive phenotype to a nonencapsulated, avirulent strain.
- This suggests the presence of non-capsular virulence factors in INT1 responsible for invasive disease.
Implications:
- These findings challenge the traditional understanding of Haemophilus influenzae virulence.
- The study implies the existence of novel, non-capsular factors that mediate invasive disease and immune evasion in NT-Hi.