Alteration of antibacterial activity of tosufloxacin and various antibacterial agents against Streptococcus pneumoniae

The minimum inhibitory concentrations (MICs) of tosufloxacin (TFLX), levofloxacin (LVFX), ciprofloxacin (CPFX), gatifloxacin (GFLX), sparfloxacin (SPFX), azithromycin (AZM), cefteram (CFTM), cefdinir (CFDN) and cefpodoxime (CPDX) against 337 clinical isolates of Streptococcus pneumoniae isolated from Japanese hospital from 1997 to 2002 were investigated by agar plate method. The incidence of penicillin-susceptible S. pneumoniae (PSSP), penicillin-intermediate resistant S. pneumoniae (PISP), and penicillin-resistant S. pneumoniae (PRSP) in each year was studied, and the MICs of antibacterial agents against these strains were determined. As the results, the total incidence of PSSP, PISP, and PRSP was 51.0%, 40.4% and 8.6%, respectively. The incidences of PSSP from 1997 to 2002 were 46.0-55.9%, and were almost definite in each year. In quinolone antibiotics, the differences of antibacterial activity among TFLX, SPFX, and GFLX against PSSP, PISP, and PRSP, were not observed, and these 3 quinolones had potent antibacterial activity. Although CPFX and LVFX showed antibacterial activity as well as other quinolones by 2001, the CPFX-resistant or LVFX-intermediate resistant strains of PSSP were seen with 56.5% and 91.3% in 2002, respectively. Thirty percents of each PSSP, PISP, and PRSP strains were AZM-resistant strains. Such tendency of increase was recognized in PSSP. Against cephem antibiotics, the incidence of intermediate resistant and resistant strains was higher for PISP and PRSP than for PSSP. No difference in the incidence of resistant strains was noted among CFTM, CFDN, and CPDX.