Antibiotic susceptibility of acute otitis media pathogens in otitis-prone Belgian children

A regional surveillance study was carried out in children with recurrent acute otitis media (AOM) to determine the antimicrobial susceptibility of three common AOM pathogens. Susceptibility to relevant antimicrobial agents was determined on 149 Streptococcus pneumoniae, 246 Haemophilus influenzae and 119 Moraxella catarrhalis strains isolated between January 1999 and January 2002, either from the nasopharynx or middle ear of 74 children with recurrent AOM, the majority (77%) being otitis-prone. Overall pneumococcal resistance to penicillin was 9.4% (6.7% penicillin-intermediate resistant, 2.7% penicillin-resistant), whereas cotrimoxazole and erythromycin resistance accounted for 25.5% and 38.9% respectively. The prevalence of antimicrobial-non-susceptible S. pneumoniae was the highest in middle ear isolates (P<0.05) and in otitis-prone children (P<0.01). Moreover, otitis-prone children harboured significantly more pneumococci resistant to at least two antimicrobial agents (24.3% versus 7.4%; P<0.01). No patient age related variation was observed. Five serogoups (6, 19, 23, 14 and 9) covered by the 7-valent pneumococcal conjugate vaccine, constituted most of the antibiotic resistant pneumococci. Among nasopharyngeal and middle ear H. influenzae isolates, 17.1% were resistant to ampicillin and 16.3% to cotrimoxazole. For M. catarrhalis, 92.4% of all isolates was ampicillin-resistant. Conclusion: this study confirms international and national differences in antimicrobial susceptibility profiles of three acute otitis media pathogens with relatively favourable antibiotic resistance rates in Belgian children with frequent acute otitis media. This at risk population of otitis-prone children is shown to harbour more antimicrobial resistant and multidrug resistant pneumococci. If antimicrobial therapy in this group of children is indicated, high dose amoxicillin is recommended whereas the use of macrolides is obsolete.Abbreviations AOM acute otitis media - MEF middle ear fluid - MIC minimal inhibitory concentration