Dynamics of pneumococcal nasopharyngeal colonization during the first days of antibiotic treatment in pediatric patients

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Abstract
Nasopharyngeal (NP) carriage of antibiotic-resistant Streptococcus pneumoniae was shown to be associated with recent antibiotic treatment. To date no studies have evaluated early dynamics of pneumococcal NP carriage during antibiotic treatment. To observe changes in NP pneumococcal carriage within 3 to 4 days after initiation of antibiotic treatment in acute otitis media (AOM). Patients ages 3 to 36 months with AOM treated with various antibiotics were prospectively followed. Nasopharyngeal culture for S. pneumoniae was obtained before (Day 1) and 72 to 96 h after initiation of treatment (Days 4 to 5). Antibiogram and serotyping were performed in all isolates as was also the MIC of penicillin. The disappearance and persistence of the initial isolates as well as the appearance of isolates with new serotype or with new antibiotic susceptibility patterns were investigated. A total of 120 patients were studied: 106 received beta-lactam antibiotics and 14 received azithromycin. Among the initial 76 pneumococcal isolates 63, 37 and 13% were resistant to ≥1, ≥2 and ≥3 antibiotic drugs. After 3 to 4 days of treatment with various beta-lactam drugs, 45, 63 and 100% of isolates with MIC values of P A rapid selection of nonsusceptible NP pneumococcal isolates during antibiotic treatment for AOM is common. This phenomenon may contribute to the spread of resistant pneumococci.