Haemophilus Meningitis

Meningitis caused by Haemophilus influenzae, historically the leading cause of bacterial meningitis in young children before the introduction of the Hib (Haemophilus influenzae type b) conjugate vaccine, which has reduced invasive Hib disease incidence by over 90% in populations with good vaccine coverage.

In unvaccinated populations, or where vaccine coverage is incomplete, it remains an important cause, predominantly affecting children under 5. Non-typeable and other capsular type strains (non-b) have become relatively more prominent in the post-vaccine era, and can also cause invasive disease, particularly in the very young, elderly, or immunocompromised.

Presentation follows the general pattern described in the Meningitis entry: fever, headache, neck stiffness, photophobia, and altered consciousness, with the specific pattern in young children often being less classic (irritability, poor feeding, lethargy, a bulging fontanelle in infants, rather than clearly localizable neck stiffness). Associated invasive Hib disease may include epiglottitis (a specific airway emergency, drooling, stridor, and respiratory distress) or septic arthritis, which can occur concurrently or independently.

Lumbar puncture with CSF analysis as detailed in the general Meningitis entry, showing a bacterial pattern (elevated opening pressure, neutrophilic pleocytosis, elevated protein, low glucose relative to serum). Gram stain may show small gram negative coccobacilli.

CSF and blood culture confirm the diagnosis and allow susceptibility testing.

Rapid antigen testing is available in some settings but has largely been superseded by culture and, increasingly, PCR based multiplex meningitis/encephalitis panels where available, given superior sensitivity and speed.

• Empirical treatment should not await confirmation and follows the general bacterial meningitis approach detailed in the Meningitis entry: ceftriaxone 2 g IV bd (adults; weight-based dosing in children, commonly 50 mg/kg bd, maximum 4 g/day), given the high prevalence of beta-lactamase producing strains that would otherwise render ampicillin ineffective
• Dexamethasone given with or just before the first antibiotic dose (0.15 mg/kg IV every 6 hours for 4 days in children, adult dosing per local protocol), given clear evidence of reduced hearing loss and neurological sequelae specifically with Hib meningitis, one of the strongest evidence bases for adjunctive steroid use across bacterial meningitis causes
• Total treatment duration typically 7 to 10 days, guided by clinical response
• Chemoprophylaxis for close contacts: rifampicin (20 mg/kg once daily for 4 days in children, 600 mg once daily for 4 days in adults) is recommended for household contacts where a vulnerable individual (unvaccinated or incompletely vaccinated child under 4, or an immunocompromised household member) is present, given the risk of secondary transmission
• Vaccination review: confirm and, where indicated, complete Hib vaccination status of the index case's close contacts, since the diagnosis often reflects a gap in vaccine coverage

Referral: infectious disease and, in children, pediatric input for all cases; ENT emergency assessment if concurrent epiglottitis is suspected, given the airway risk.