Haemophilus influenzae is a gram negative coccobacillus (short rod), which is non-motile, capsular and ong thread-like and pleomorphic in CSF specimen.
Route of Entry
H. influenzae infects humans only. It enters through the upper respiratory tract.
After entry of the organism, there are two fates:
• Asymptomatic colonization
The organism produces IgA protease, which breaks down secretory IgA, therefore facilitating attachment to the respiratory mucosa.
Encapsulated variety enters blood stream and spreads to meninges. Non- encapsulated variety causes local infections.
The capsule of most lethal varieties is composed of polyribitol phosphate and is antiphagocytic. Endotoxin is lipopolysaccharide.
• IgA protease
• Childrens 6 months to 6 years of age
Symptoms of invasive infections include:
- Stiff neck
Symptoms of local infections include:
• Otitis media
• Nasopharyngeal specimen
Features observed under microscope include:
• Gram negative coccobacillus
• Long thread-like and pleomorphic in CSF specimen
Chocolate agar plus factor X (heme compound) plus factor V (NAD)
Mucoid colonies are formed. Factor X is required to produce essential enzymes e.g cyctochromes, catalases, peroxidases. Factor V is an electron carrier.
Biochemical tests are not usually done. B-biotypes are differentiated by indole, urease and ornithine decarboxylase tests.
• Quelling reaction
• Fluorescent- antibody staining
• Latex agglutination test.
- In case of local infection –amoxicillin– clavulanate is given.