Role of nontypeable Haemophilus influenzae in pediatric respiratory tract infections.

Nontypeable strains of Haemophilus influenzae may spread contiguously from the upper respiratory tract and cause sinusitis, otitis media and pneumonia. Unlike H. influenzae type b these strains rarely invade the bloodstream to cause widespread infections. These strains are primary pathogens of acute otitis media, sinusitis and the conjunctivitis-otitis syndrome. In developing countries these strains are also responsible for many cases of pediatric pneumonia. Currently approximately 30% of nontypeable H. influenzae strains are beta-lactamase-positive and can inactivate susceptible penicillins, including penicillins G and V, ampicillin and amoxicillin. Most second generation oral cephalosporins are active against beta-lactamase-producing H. influenzae. Some third generation oral cephalosporins, e.g. cefixime, however, have particularly good efficacy against H. influenzae. Sulfonamides and chloramphenicol are generally effective as well. Until a vaccine that provides adequate prophylaxis against nontypeable H. influenzae is developed, clinicians should be guided by knowledge of bacterial susceptibility and microbiologic efficacy in choosing appropriate agents for treating pediatric infections likely to involve this common pathogen.