Haemophilus Summary

Haemophilus influenzae:

  Normal indigenous microflora of human upper respiratory tract

  Gram-negative bacilli requiring blood for growth (see WebLinked image; see WebLinked image)

  Strains associated with acute pediatric infections of sites other than upper respiratory tract (e.g., meningitis, epiglottis, conjunctivitis, arthritis, cellulitis) are encapsulated (can demonstrate with Quellung reaction). Indigenous flora of the upper respiratory tract and thoses organisms that infect this site (otitis media, sinusitis, bronchitis) do not have a capsule.

  Six capsular serotypes of which type b causes virtually all human disease, specific anti-capsular antibody is protective.

  Marked host specificity, each species of the genus is associated with a specific host

  Most common cause of acute bacterial meningitis in infants and young children, as well as, other serious pediatric diseases, e.g., epiglottis, cellulitis

  Chronic pulmonary disease in adults

  Grown on chocolate agar; blood is heated to inactivate inhibitors and to release factors from red blood cells required for growth of organisms; requirement for heat-labile V-factor (NAD, NADP coenzymes) and heat-stable X-factor (precursor of hemin)


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