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Potentiation of experimental meningitis due to Haemophilus influenzae by influenza A virus
Abstract:
When Haemophilus influenzae type b was given intranasally to infant rats, a very large dose was required to produce histologic evidence of meningitis in even half of the animals tested; meningitis developed in 16 of 31 rats that received 10(7) viable bacteria at the age of five days. However, when the animals first received influenza virus, the dose of bacteria required to produce meningitis was reduced 100-fold; meningitis occurred in 10 of 21 rats given virus at two days and 10(5) viable bacteria at five days. These results suggest that prior viral infection of the upper respiratory tract may be a factor in the pathogenesis of haemophilus meningitis.
Insights
Prior influenza virus infection significantly reduces the bacterial dose of Haemophilus influenzae type b needed to cause meningitis in infant rats. This suggests viral infections may precede bacterial meningitis development.
Area of Science:
- Microbiology
- Virology
- Pathogenesis
Background:
- Haemophilus influenzae type b (Hib) is a significant cause of bacterial meningitis.
- The pathogenesis of Hib meningitis, particularly in infants, requires further elucidation.
Purpose of the Study:
- To investigate the potential role of prior viral infection in the susceptibility to Haemophilus influenzae type b meningitis.
Main Methods:
- Infant rats were inoculated intranasally with Haemophilus influenzae type b (Hib).
- A separate group of infant rats received influenza virus prior to Hib inoculation.
- Meningitis incidence and bacterial dose required were compared between groups.
Main Results:
- A high dose of Hib (10^7 bacteria) was needed to induce meningitis in 51% of rats without prior viral infection.
- Prior influenza virus infection reduced the required Hib dose by 100-fold (10^5 bacteria) to cause meningitis in 47% of rats.
- These findings indicate a synergistic effect between viral and bacterial infections.
Conclusions:
- Prior viral infection of the upper respiratory tract may increase susceptibility to Haemophilus influenzae type b meningitis.
- Influenza virus infection could be a predisposing factor in the development of bacterial meningitis.