Genetic relationship of penicillin resistant Streptococcus pneumoniae serotype 19B strains in Japan

Pulsed field gel electrophoresis (PFGE) of the genomic DNA of penicillin resistant serotype 19B Streptococcus pneumoniae was carried out. Thirteen strains form the Nagasaki area and 12 strains from other areas in Japan were examined. Twenty-three strains were resistant to erythromycin, tetracycline and trimethoprim/sulfamethoxazole but susceptible to chloramphenicol. Eight strains were resistant to ceftriaxone. All strains were multiply resistant. Five strains isolated from Nagasaki were indistinguishable from each other by using restriction enzymes Apa I and Sma I. Two strains isolated from other areas were indistinguishable from the above five strains. We could classify 13 Nagasaki strains into 3 groups and the total of 25 Japanese strains into 6 groups. These results suggest that the increasing prevalence of multiply drug resistant S. pneumoniae serotyped 19B in Japan is not due to a single clone, but at least one clone has spread widely in Japan.