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Updated: Oct 21, 2026
05:57
In Vitro Assay of Bacterial Adhesion onto Mammalian Epithelial Cells
Published on: May 16, 2011
Occurrence of pili on and adhesive properties of Haemophilus parainfluenzae
Journal of Bacteriology
|February 1, 1981
Abstract:
Of 20 clinical isolates of Haemophilus parainfluenzae, 13 produced a mannose-resistant hemagglutinin that agglutinated erythrocytes from chickens, horses, rabbits, and sheep. Examination with the electron microscope showed that only strain HR-885 was pilate. Grown in static liquid culture, the 12 hemagglutinating, nonpilate isolates formed small, tightly packed clumps, whereas strain HR-885 formed large, loosely packed clumps. However, seven isolates did not produce a hemagglutinin, did not clump, and were nonpilate.
Insights
Most Haemophilus parainfluenzae isolates produce hemagglutinins, affecting erythrocyte agglutination. Piliated strains form distinct clumps in culture, differentiating them from non-piliated variants.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Cellular Morphology
Background:
- Haemophilus parainfluenzae is a species of Gram-negative coccobacillus.
- Hemagglutinins are cell surface proteins that bind to red blood cells, mediating agglutination.
- Pili are hair-like appendages on bacteria involved in adhesion and biofilm formation.
Purpose of the Study:
- To investigate the presence and function of hemagglutinins in clinical isolates of Haemophilus parainfluenzae.
- To correlate hemagglutinin production with bacterial morphology, specifically pilation and clumping behavior.
Main Methods:
- Isolation and culturing of 20 clinical strains of Haemophilus parainfluenzae.
- Assay for mannose-resistant hemagglutinin activity against various erythrocytes (chicken, horse, rabbit, sheep).
- Electron microscopy to determine the presence or absence of pili (pilate vs. nonpilate).
- Observation of bacterial clumping in static liquid culture.
Main Results:
- Thirteen of 20 isolates produced mannose-resistant hemagglutinins, agglutinating erythrocytes from multiple animal species.
- Only one isolate (HR-885) was found to be pilate via electron microscopy.
- Pilate strain HR-885 formed large, loosely packed clumps, while 12 hemagglutinating, nonpilate isolates formed small, tightly packed clumps.
- Seven isolates lacked hemagglutinin production, did not clump, and were nonpilate.
Conclusions:
- Mannose-resistant hemagglutinin production is common in clinical isolates of Haemophilus parainfluenzae.
- Bacterial pilation is associated with distinct clumping characteristics in liquid culture.
- A subset of Haemophilus parainfluenzae isolates lacks hemagglutinin production and pili, suggesting diverse phenotypic expressions within the species.
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