Bacterial epidemiology of nasopharyngeal flora in children with acute otitis media

A french national epidemiological study of nasopharyngeal flora has been carried out in a community during the winter of 1994-1995 in 630 children suffering of acute otitis media. A total of 856 bacterial strains has been isolated from nasopharyngeal secretions, the three main pathogens being Haemophilus influenzae (31.9% of isolates), Streptococcus pneumoniae (31.3%), and Moraxella catarrhalis (24.1%). The overall nasopharyngeal carriage rate for H. influenzae and that of serotype b strains were respectively 43.3% and 11.6%. Thirty per cent of H. influenzae strains were beta-lactamase producers and 3.2% were ampicillin-resistant though did not produce beta-lactamase. The nasopharyngeal carriage rate for S. pneumoniae was 42.5% and that of serotype 23 strains was 8.1%. Among the pneumococci, 38.8% of strains showed reduced susceptibility to penicillin (PRSP), the majority of these strains (69%) being intermediate resistant to penicillin (MIC 0.1-1mg/l). More than one-third (37.5%) of PRSP strains were serotype 23, other resistant serotypes were mainly serotype 14, 19, 9 and 6. Analysis of the distribution of PRSP strains showed that this resistance phenomenon concerned all of France. However large variations in regional distributions of PRSP and beta-lactamase-producing H. influenzae were noted : a high incidence (> 50%) of PRSP was observed in Paris area, Normandy and southeastern France. Similarly, the proportion of H. influenzae isolates that were beta-lactamase producers varied between the regions with an overall incidence of 30.4% : a high incidence (greater than or equal to 40%) was observed in Paris area and Normandy, but also in Champagne-Ardennes et in northern France. The emergence of PRSP strains and the rapid growth of this phenomenon worlwide in the past few years calls into question the classical antibiotic therapy of acute otitis media, especially as these pneumococcal and H. influenzae strains are often multiresistant (macrolides, cotrimoxazole...). The evidence for geographical variations in the incidence of PRSP and beta-lactamase-producing H. influenzae argues for therapeutic policies adapted to the regional epidemiology. Diversification of first-line antibiotic therapy can only have beneficial effects in terms of cost and bacterial ecology.