Intermediate resistance of streptococcus pneumoniae to penicillin in children in day-care centers

This study was performed to determine the prevalence, serotypes and antibiotic susceptibility patterns of penicillin-resistant Streptococcus pneumoniae in children younger than 3 years of age in day-care centers in Houston, TX. Nasopharyngeal cultures were obtained on two occasions, in March and May, 1989, from 140 children in 4 day-care centers. All penicillin-resistant S. pneumoniae organisms isolated in this study had minimum inhibitory concentrations to penicillin of between 0.1 and 0.5 μg/ml and were thus intermediately resistant. No highly resistant S. pneumoniae (minimum inhibitory concentration ≥1.0 μg/ml) was isolated in this study. Nasal carriage of S. pneumoniae occurred in 39% of children; carriage of intermediately resistant S. pneumoniae occurred in 4% of children. Of the 39% of children who carried S. pneumoniae, 11% carried intermediately resistant strains. In one day-care center with a prior history of intermediately resistant S. pneumoniae (Center 1), the prevalence of intermediate penicillin resistance was significantly (P = 0.047) higher than in the other three centers. Among children surveyed twice 15% of Center 1 children carried an intermediately penicillin-resistant strain at least once, whereas in the other centers 3% of children carried an intermediately resistant strain at least once. Sixty-two percent of intermediately penicillin-resistant strains were resistant to multiple antibiotics and all were serotype 14. Intermediately penicillin-resistant S. pneumoniae isolates were prevalent among young children in day-care centers in Houston and may persist in some day-care centers and become endemic.