What causes of Haemophilus influenzae infections?

Updated: Jun 11, 2021
  • Author: Joseph Adrian L Buensalido, MD; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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Bacteremia precedes Hib meningitis and other invasive Hib diseases. Direct extension of infection from the sinuses or ears is rare. The magnitude and duration of bacteremia are the primary determinants of CNS invasion, which occurs via the choroid plexus. The magnitude of the CSF bacterial density correlates with the severity of the disease. Morbidity and mortality associated with meningitis result from inflammation, edema, and increased CSF pressure. Brain parenchymal invasion is rare.

In epiglottitis, Hib invades the epiglottis and supraglottic tissues, causing cellulitis and swelling that causes the epiglottis to curl posteriorly and inferiorly over the airway, thus obstructing airflow during inspiration but allowing normal expiration. An acute airway obstruction follows.

Invasive H influenzae disease in neonates is rare and is caused most often by NTHi strains. This condition is associated with premature birth, premature rupture of membranes, low birth weight, and maternal chorioamnionitis. Transmission occurs through the maternal genital tract. NTHi biotype 4 can colonize the genital tract and is a major cause of invasive disease.

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