Individual use of antibiotics and prevalence of beta-lactamase production among bacterial pathogens from middle ear fluid

Prescription data and clinical laboratory data were analysed to assess the influence of previous antibiotic therapy on the prevalence of beta -lactama se in isolates of Haemophilus influenzae and Moraxella catarrhalis from pri mary specimens of middle ear fluid from 2129 children aged 0-5 years. The p revalence of beta -lactamase-positive H. influenzae was 6.6% [95% confidenc e interval (CI): 3.5-9.8%] in children who received antibiotics 5-90 days b efore isolation of the organism compared with 7.0% (95% CI: 3.9-10.2%) in t hose who did not. The prevalence of beta -lactamase-positive M. catarrhalis was 90.9% (95% CI: 84.0-97.8%) in children who received antibiotics compar ed with 86.7% (95% CI: 79.0-94.4%) in those who did not.