Nasopharyngeal Streptococcus pneumoniae carriage in Japanese children attending day-care centers.

OBJECTIVES

We conducted a prospective bacteriological survey to investigate antibiotic resistance-related genetic characteristics and the turnover of nasopharyngeal Streptococcus pneumoniae carriage in healthy children in day-care centers (DCCs).

METHODS

A total of 363 nasopharyngeal mucus samples were collected from children aged 0 to 6 years attending two DCCs in the summer of 2004 (n=181) and the following winter (n=182). We obtained 157 S. pneumoniae isolates and analyzed them by antibiotic susceptibility testing, PCR assay for the penicillin-binding protein (PBP) genes and macrolide-resistance gene, and pulsed-field gel electrophoresis (PFGE).

RESULTS

The overall carriage rate was 43.3% (157/363). The percentages of penicillin-intermediately resistant S. pneumoniae (PISP) strains, penicillin-resistant S. pneumoniae (PRSP) strains, erythromycin-intermediately resistant S. pneumoniae strains and erythromycin-resistant S. pneumoniae strains were 35.7% (56/157), 0.6% (1/157), 1.9% (3/157), and 69.4% (109/157), respectively. The percentages of S. pneumoniae strains with the pbp mutation(s) and mefA and/or ermB gene(s) were 92.4% (145/157) and 71.3% (112/157), respectively. Fifty strains with different PFGE patterns were obtained from among the 157 isolates. Thirteen strains were observed in both seasons, but only one of these strains was isolated from the same carrier. Twenty-one strains (42.0%) were isolated from two or more children, and 17 of these were each isolated from children attending the same DCC.

CONCLUSIONS

These results indicate the spread of S. pneumoniae, particularly those with antibiotic-resistance genes, and the vigorous genetic turnover and substantial horizontal transmission of this pathogen in healthy children attending DCCs in Japan.