Emergence of antibiotic resistant Streptococcus sanguis in dental plaque of children after frequent antibiotic therapy.

In the pediatric population, several different antibiotic regimens are currently recommended for the treatment of otitis media. This study investigated whether therapy for otitis media was associated with the emergence of antibiotic-resistant oral bacteria. Streptococcus sanguis (S. sanguis) was isolated from supragingival dental plaque of children after a recent course of antibiotic. The isolated strains were tested for resistance to penicillin, amoxicillin, trimethoprim-sulfamethoxazole, and erythromycin and compared to isolated strains from age- and sex-matched control subjects, who had received no antibiotics within two years before sampling. While control subjects harbored no resistant strains of S. sanguis, about 60% of children who had received antibiotics harbored S. sanguis which were resistant to at least one of the tested antibiotics. Nearly half of these strains were resistant to two or more antibiotics. Resistance to penicillin and amoxicillin decreased with the age of the child and with the length of time since exposure to the antibiotic. However, resistance to trimethoprim-sulfamethoxazole or erythromycin showed no relationship to the age of the child or the length of time since exposure to the antibiotic. The data show that children who had been treated for otitis media with common antibiotic protocols do harbor antibiotic-resistant oral streptococci which may complicate prophylactic and therapeutic regimens for bacterial endocarditis.