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Biotype of Haemophilus influenzae: correlation with virulence and ampicillin resistance
Abstract:
Biotype and serotype were determined for 473 isolates of Haemophilus influenzae from 399 children. Patients with invasive disease usually had serotypable (86%) and biotype 1 (80%) isolates. Respiratory isolates from well children and children whose illness was not caused by H. influenzae were rarely serotypable (1%) or biotype 1 (8%). Respiratory isolates from children whose illness was possibly or probably related to H. influenzae and isolates from children with cystic fibrosis were more frequently biotype 1, serotypable, or both (P less than 0.01 for all comparisons). Ten (67%) of 15 children with acute otitis media due to H. influenzae had tympanocentesis isolates which were biotype 1; only one isolate was serotypable. Isolates from inflamed conjunctivae had biotypes and serotypes similar to respiratory isolates from well children. Ampicillin resistance was less frequent among biotype 1 isolates (9%) compared with other biotypes (19%) (P less than 0.01). The data suggest that H. influenzae is biochemically heterogeneous and that noncapsular factors, frequently predictable by biotype, contribute to virulence.
Insights
Haemophilus influenzae biotypes and serotypes vary by disease. Biotype 1 and serotypable isolates are common in invasive disease, while other types are linked to respiratory infections and cystic fibrosis.
Area of Science:
- Microbiology
- Pediatric Infectious Diseases
Background:
- Haemophilus influenzae is a significant pathogen in children.
- Understanding the biochemical and serological characteristics of H. influenzae is crucial for diagnosing and treating infections.
Purpose of the Study:
- To investigate the association between biotype, serotype, and clinical presentation of Haemophilus influenzae isolates from children.
- To determine if specific biotypes and serotypes correlate with disease severity and ampicillin resistance.
Main Methods:
- Biochemical (biotyping) and serological (serotyping) characterization of 473 H. influenzae isolates from 399 children.
- Correlation of isolate characteristics with clinical data, including disease type (invasive, respiratory, otitis media, conjunctivitis) and patient status (well, cystic fibrosis).
Main Results:
- Invasive H. influenzae disease was predominantly associated with serotypable (86%) and biotype 1 (80%) isolates.
- Respiratory isolates from well children or those with non-H. influenzae illness were rarely serotypable (1%) or biotype 1 (8%).
- Isolates from children with H. influenzae-related respiratory illness, cystic fibrosis, or acute otitis media showed a higher prevalence of biotype 1 and/or serotypability (P < 0.01).
- Ampicillin resistance was lower in biotype 1 isolates (9%) compared to other biotypes (19%) (P < 0.01).
Conclusions:
- Haemophilus influenzae exhibits significant biochemical heterogeneity.
- Biotype, often predictable, appears to be a key factor in H. influenzae virulence, independent of capsular type.
- These findings highlight the importance of biotyping for understanding H. influenzae pathogenesis and guiding treatment decisions.