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Nontypable Haemophilus influenzae are unencapsulated both in vivo and in vitro

F Gyorkey, D Musher, P Gyorkey

    The Journal of Infectious Diseases
    |April 1, 1984
    PubMed

    Insights

    Nontypable Haemophilus influenzae lack a capsule, unlike typable strains, even when found in patients with pneumonia. This suggests nontypable strains are not simply encapsulated variants that lost their capsule in vitro.

    Area of Science:

    • Microbiology
    • Bacterial Pathogenesis
    • Respiratory Infections

    Background:

    • Nontypable Haemophilus influenzae (NTHi) are a significant cause of respiratory infections in adults.
    • It has been hypothesized that NTHi may originate from encapsulated, typable strains that have lost their capsule during in vitro cultivation.

    Purpose of the Study:

    • To investigate the presence of capsular glycocalyx in both typable and nontypable Haemophilus influenzae.
    • To determine if NTHi found in clinical samples are indeed unencapsulated variants of typable strains.

    Main Methods:

    • Electron microscopy combined with ruthenium-red staining was employed.
    • Analysis of H. influenzae colonies grown in vitro.
    • Examination of bronchopulmonary secretions from patients with H. influenzae pneumonia or tracheobronchitis.

    Main Results:

    • Typable H. influenzae (types a, b, e') exhibited a detectable capsular glycocalyx, both in vitro and in clinical specimens.
    • Nontypable H. influenzae consistently appeared unencapsulated, irrespective of whether they were grown in vitro or directly observed in patient secretions.

    Conclusions:

    • Nontypable Haemophilus influenzae lack a detectable capsule, challenging the hypothesis that they are simply encapsulated strains that have lost their capsule.
    • The findings suggest that NTHi may represent a distinct category of H. influenzae with inherent unencapsulated characteristics.

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