Antibiotic susceptibility according to genotype of penicillin-binding protein and macrolide resistance genes, and serotype of Streptococcus pneumoniae isolates from community-acquired pneumonia in children

Objectives: Antibiotic susceptibilities, genes mediating β-lactam and macrolide resistance, and serotypes were analysed for strains of Streptococcus pneumoniae. Methods: A total of 392 strains of S. pneumoniae were isolated from paediatric patients with community-acquired pneumonia between May 2002 and 2004. All strains were classified into six genotype patterns according to the mutations found in the pbp1a, pbp2x and pbp2b genes identified by PCR. These results are represented by adding 'g', indicating genotypic identification. Results: Thirty-nine percent of the isolates showed mutations in either one or two PBP genes (gPISP, where PISP stands for penicillin-intermediate resistant S. pneumoniae) and 52.3% had mutations in three genes (gPRSP, where PRSP stands for penicillin-resistant S. pneumoniae). The majority of the strains had a macrolide resistance gene: mef(A), (30.6%); erm(B), (48.5%); or both mef(A) and erm(B), (7.7%). The most frequent serotypes of these strains were: 6B (23.2%), 23F (17.6%), 19F (17.3%), 14 (10.5%) and 6A (8.2%). Serotypes of the seven-valent conjugate vaccine covered 70.9% of all isolates, and 89.8% of gPRSP. Serotypes of the strains with cefotaxime MICs of ≥2 mg/L were almost all of a vaccine type. Conclusions: The results suggest that introduction of conjugate vaccines into infants and children is necessary for the prevention of pneumococcal infections in Japan.