[Population biology of Streptococcus pneumoniae carried by healthy children in Shanghai].

OBJECTIVE To investigate the population biology of Streptococcus pneumoniae carried by healthy children. METHODS Drug resistant patterns and serotypes of 222 strains were determined. PFGE, BOX PCR and pbp fingerprint techniques were used to analyze the homology among strains. RESULTS Among 222 nasopharyngeal isolates from 5 day-care centers, there were 32 penicillin intermediate Streptococcus pneumoniae (PISP, MIC 0.125 approximately 1 mg/L), and no penicillin resistant Streptococcus pneumoniae (PRSP, MIC >/= 2 mg/L) was found. The main serotypes of all strains were 23F (25.7%), 6A (13.1%), 19F (10.8%), and 6B (8.1%). The serotypes of PISP were mainly 23F (50%), 19A (15.6%) and 19F (15.6%). Among the 32 PISP strains, 8 BOX PCR clusters and 7 PFGE types were identified. The resistance patterns, serotypes, BOX PCR and pbp fingerprints of PFGE type A strains were highly consistent. In day care center (DCC) SY, the penicillin resistant rate was 31.8%, being much higher than the average level. Twenty of the 21 PISP strains isolated from this DCC belonged to PFGE type A or B. CONCLUSIONS The penicillin resistant rate of Streptococcus pneumoniae carried by healthy children in 5 DCCs of Shanghai was still low. However in one DCC, there could be a prevalence of some resistant clones which resulted in high penicillin resistant rate.