Bacterial epidemiology of acute otitis media in children

Acute otitis media are very frequent in children under 5 years of age. Following viral infection, bacterial species belonging to the nasopharyngeal flora colonize the middle ear mucosa. The predominant species are H. influenzae, S. pneumoniae and M. catarrhalis. Acute otitis media are usually benign, but rare complications may develop such as mastoiditis, meningitis, or sequelae (deafness). The recent emergence of pneumococci resistant to penicillin G in France has altered classical antibiotherapy based on penicillin G or its derivatives. In fact, the geographical distribution of resistant pneumococci is heterogeneous, with highly endemic areas and almost unaffected regions. Almost 37 % of pneumococci isolated from the nasopharyngeal flora of children display an abnormal susceptibility to penicillin G (MIG > 0.1 mg/l), including a significant percentage of strains with MIC > 1 mg/l. Most resistant isolates belong to serotypes 19 and 23 F. The antibiotic susceptibility of H. influenzae is stable for several years. Almost 30 % of isolates are beta-lactamase-producers and 10-15 % serotype b of isolates belong to the invasive. M. catarrhalis is responsible for 10 % of acute otitis, often in association with other bacteria. Most isolates produce beta-lactamases, but this pathogen remains usually susceptible to the classical antibiotherapy. Antibiotic resistance is a rapidly evolutive, dynamic phenomenon. The probabilistic antibiotherapy must be based on the knowledge oi the regional epidemiology and diversified to reduce the selective pressure of antibiotics.