Haemophilus influenzae, a small pleiomorphic gram-negative coccobacillus, is a common inhabitant of the upper respiratory tract in 20%–50% of healthy adults and 80% of children. H influenzae is 1 of the 3 organisms responsible for most cases of bacterial meningitis. Roughly 14% of patients with meningitis develop significant neurologic damage. Other infections caused by this organism include orbital cellulitis, epiglottitis, arthritis, otitis media, bronchitis, pericarditis, sinusitis, and pneumonia. A DNA PCR probe assay can be used for rapid diagnosis of the most virulent strain, H influenzae type b (Hib) infections.
Treatment of acute H influenzae infections has been complicated by the emergence of β-lactamase strains, with an incidence approaching 50% in some geographic areas. Current recommendations are to treat with third-generation cephalosporins, which are highly effective against H influenzae infections. Alternative treatments include meropenem or ampicillin and chloramphenicol. Nearly all isolates of H influenzae are resistant to macrolides. Serious or life-threatening infections should be treated with an intravenous third-generation cephalosporin with known activity against H influenzae, such as ceftriaxone or cefotaxime, pending results of sensitivity testing.
Hib conjugate vaccines are available for use in infants and have shown their effectiveness in protecting infants and older children against meningitis and other invasive diseases caused by Hib infection. The incidence of meningitis, orbital cellulitis, and other infections caused by Hib has been reduced significantly since Hib conjugate vaccines became available. However, it is important to remember that immunized patients are still susceptible to infections caused by strains of H influenzae other than type b.
Davis S, Feikin D, Johnson HL. The effect of Haemophilus influenzae type B and pneumococcal conjugate vaccines on childhood meningitis mortality: a systematic review. BMC Public Health. 2013;13(Suppl 3):S21.
Excerpted from BCSC 2020-2021 series: Section 1 - Update on General Medicine. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.