[Epidemiological analysis of Streptococcus pneumoniae in Gifu prefecture]

Since antimicrobial resistance in Streptococcus pneumoniae become serious problem, we have conducted the epidemiological analysis of Streptococcus pneumoniae in Gifu prefecture. We have investigated the mutations of penicillin-binding protein (PBP) cording genes, the mutations of macrolide-resistant cording genes, and antimicrobial susceptibility using broth microdilution method, for 345 strains isolated from clinical specimens between May 2006 and July 2006 at 12 clinical facilities of 5 medical area. The ratio of penicillin-susceptible S. pneumoniae (gPSSP), penicillin-intermediate S. pneumoniae (gPISP), and penicillin-resistant S. pneumoniae (gPRSP), which were judged by molecular techniques, were 7.2%, 53.5%, and 39.4%, respectively. Only 1 gPSSP strain was isolated from children under three years old. There have been regional differences of the isolation rate of gPRSP between Gifu/Chuno area (55-60%) and Tono/Hida area (23-32%) in second- or third-medical facilities. The isolation rate of PBP mutation genes, pbp2x, pbp1a and pbp2b, were 92.8%, 52.5% and 53.3%, respectively. The isolation rate of macrolide-resistant cording genes, mefA only, ermB only, and both mefA and ermB, were 30%, 50% and 8%, respectively. The strains of S. pneumoniae with both mefA and ermB mutations, increased from 4% in 2002 to 8% in 2006. The antimicrobial susceptibility of S. pneumoniae to penicillin G (PCG) showed two peaks around 0.03 and 1 microg/mL, and 89% of S. pneumoniae with minimum inhibitory concentration (MIC) value 1 microg/mL was gPRSP. The MIC values of PCG against 69% strains of gPRSP distributed between 0.25 and 1 microg/mL. There have been the decreased tendency for the differences among medical facilities in penicillin resistant strains. Although cefditoren showed the most effective antimicrobial activity in oral cephems tested, there have been the strains with MIC value of over 1 microg/mL. The MIC90 of panipenem was 0.125 microg/mL, which was the best antimicrobial activity in carbapenems. The resistant rates of clarithromycin and azithromycin were 85% and 84%, respectively. The strains with the gene mutation of ermB have showed resistant to clindamycin. The MIC90 of tosufloxacin was 0.25 microg/mL, which was the best antimicrobial activity in quinolones. We have detected 4 levofloxacin highly resistant S. pneumoniae, of which MIC value was over 32 microg/mL. Also, we have encountered the episode of the spread of S. pneumoniae in one family, which was clarified by scientific approach.