Members of the genus Haemophilus require certain growth factors present in blood (haemophilic) for their growth


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

Diagnosis of H. influenzae infections :- Pathological material e.g. pus, sputum or CSF is examined as follows

 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


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