This organism is often found in normal throats. Capsulated strains cause meningits and epiglottitis in children. It also, causes respiratory disease complications (bronchitis , pneumonia , otitis media and sinusitis ) in patients having viral influenza
Morphology:- Gram negative small coco-bacilli; long filamentous and pleomorphic forms occur. Many strains are capsulated
Cultural characters: They are facultative anaerobes and require for their growth heated blood containing media; chocolate agar provide haematin ( X factor ) and diphosphopyridine nucleotide ( V factor ( which are essential for growth. Colonies are small and transparent, those growing near Staph, aureus growth are large and dense since staphylococci produce V factor. This is called satellitism
Serological characters: Smooth capsulated strains can be classified into 6 types depending on the capsular polysaccharide. H. influenzae type b ( Hib ) is the most pathogenic
Smears are stained with Gram. When the organism is present in large numbers in specimens , it can be directly detected by Quellung capsule swelling reaction, immunofluorescence or PCR
Specimens are inoculated on chocolate agar at 37C in 5% CO2 . Colonies are identified by their morphology, inability to grow except on blood containing media, and serologically type with specific antisera Satellitism around a disc containing XV factors helps in their detection in a mixed culture
Direct detection of H. influenzae polysaccharide antigen in CSF by latex slide agglutination or coagglutination commercial kits
