Acute otitis media
Acute otitis media is a bacterial infection of the mucosally lined air-containing spaces of the temporal bone. Purulent material forms not only within the middle ear cleft but also within the pneumatized mastoid air cells and petrous apex.
Acute otitis media is usually precipitated by a viral upper respiratory tract infection that causes eustachian tube obstruction. This results in accumulation of fluid and mucus, which becomes secondarily infected by bacteria. The most common pathogens are Streptococcus pneumoniae, Haemophilus influenzae, and Streptococcus pyogenes.
Because the fluid of the middle ear is seeded by organisms of the upper respiratory tract, it is not surprising that the bacteria that commonly cause acute otitis media are Streptococcus pneumoniae
Currently, controversy exists regarding whether all children with acute otitis media should receive antimicrobial therapy. Some experts feel that children 2 years of age and older without severe symptoms at presentation may be treated symptomatically for 48 to 72 hours. If improvement occurs, these children may not require antibiotics. Other experts suggest that all children with acute otitis media should receive antibiotics. When treatment is indicated, it is empiric because cultures of middle ear fluid are infrequently obtained in uncomplicated acute otitis media.
High-dose amoxicillin is first-line therapy for acute otitis media. At first glance, this agent appears to be an odd choice for the treatment of an infection caused by bacteria that are often penicillin resistant. When given in high doses, however, amoxicillin achieves levels in the middle ear fluid that exceed the minimal inhibitory concentrations of all but the most highly penicillin-resistant S. pneumoniae strains. Although many strains of H. influenzae and M. catarrhalis produce β-lactamases that degrade amoxicillin, clinical studies have demonstrated resolution in many cases of amoxicillin-treated otitis media caused by these two pathogens.
Some experts recommend that patients at risk for infection caused by amoxicillin resistant bacteria (e.g., children recently treated with β-lactam antibiotics; children with purulent conjunctivitis, which is usually caused by β-lactam-resistant H. influenzae) be treated with amoxicillin/clavulanate. In patients who have mild (non– type I hypersensitivity) allergic responses to amoxicillin, oral cephalosporins (cefdinir, cefpodoxime, cefuroxime) may be used. In those with type I hypersensitivity reactions (urticaria or anaphylaxis) to penicillins, macrolides (azithromycin