Antibacterial activity of tosufloxacin against fresh clinical isolates

The antibacterial activity of tosufloxacin (TFLX) was compared with those of other new quinolones (ofloxacin, ciprofloxacin, sparfloxacin and fleroxacin) against clinical isolates. These isolates had been collected from May to June 1993 (22 species, 260 strains) and from June to July 1992 (Staphylococcus aureus and Pseudomonas aeruginosa, 87 strains) in Toyama municipal hospital. TFLX showed the most potent activities against methicillin-susceptible S. aureus, methicillin-susceptible Staphylococcus epidermidis, methicillin-resistant S. epidermidis, Enterococcus faecalis and Escherichia coli in 1993, at MIC50 levels. The MIC50's of TFLX for these species ranged from 0.025 to 0.39 microgram/ml. TFLX showed potent activities against Klebsiella pneumoniae and P. aeruginosa, and the MIC50's of TFLX were 0.05 and 0.39 microgram/ml, respectively. However, new quinolone resistant strains (MIC > or = 6.25 micrograms/ml) were found among some species. Especially, the number of methicillin-resistant S. aureus (MRSA) strains resistant to new quinolone exceeded 60% of all the S. aureus isolates in 1993. More MRSA strains resistant to new quinolones were isolated in 1993 than in 1992, and similar result was observed for P. aeruginosa. The coagulase typing was done, and all MRSA strains of resistant to new quinolones produced coagulase type II.