Haemophilus influenzae infections in adults: a pathogen in search of respect.

Despite the success of Haemophilus influenzae type b vaccines in preventing bacterial disease in children, H influenzae remains a common pathogen in adult patients in the United States and Europe. At least half of invasive H influenzae infections are caused by nontypable strains. The spectrum of diseases includes sinusitis, pneumonia, otitis media, epiglotitis, and meningitis. An etiologic diagnosis is most reliably established by positive cultures from a normally sterile site. Although resistance to ampicillin and amoxicillin has steadily increased in clinical H influenzae isolates during the past two decades, a variety of other antimicrobial agents are available for the treatment of infections caused by this bacterium.