Antimicrobial susceptibility of Streptococcus pneumoniae isolated from pediatric carriers in Spain.

The in vitro activity of several beta-lactam agents, macrolides, and cotrimoxazole was investigated against 53 Streptococcus pneumoniae isolates recovered from healthy children. The rates of resistance to penicillin or amoxicillin, cefaclor, and cefuroxime were 30%, 51%, and 37%, respectively. No cefotaxime-resistant isolates were found. Rates of resistance to erythromycin, clarithromycin, and cotrimoxazole were 22.6%, 13.2%, and 83%, respectively. Pneumococci with divergent antimicrobial susceptibility profiles (susceptible or moderately resistant vs. resistant isolates) coexisted in 32% samples, with divergencies more often involving beta-lactam agents and/or macrolides. In five of these samples, isolates belonged to different serotypes.