NORTH-AMERICAN (UNITED-STATES AND CANADA) COMPARATIVE SUSCEPTIBILITY OF 2 FLUOROQUINOLONES - OFLOXACIN AND CIPROFLOXACIN - A 53-MEDICAL-CENTER SAMPLE OF SPECTRA OF ACTIVITY

Ofloxacin, a newer broad-spectrum fluoroquinolone, was evaluated again st > 12,000 clinical isolates in a multicenter surveillance trial in t he United States and Canada using the standardized disk diffusion meth od. A total of 53 geographically diverse clinical microbiology laborat ories contributed zone diameter results for ofloxacin, ciprofloxacin, and norfloxacin for urinary tract infection (UTI) isolates; and ofloxa cin and ciprofloxacin for respiratory tract infection (RTI) isolates, skin and soft tissue infection (SSTI) isolates, and genital tract path ogen isolates. In both the USA and Canada, ofloxacin was shown to have the wide spectrum of activity as follows: RTI isolates, ofloxacin (92 .2%-93.8% susceptible), ciprofloxacin (89.5%-90.4%); SSTI isolates, of loxacin (87.1%-93.6%) > ciprofloxacin (78.8%-90.4%); UTI isolates, ofl oxacin (91.6%-92.5%) > norfloxacin (87.3%-91.7%) > ciprofloxacin (86.4 %-89.7%); and genital tract isolates, ofloxacin (94.0%) > ciprofloxaci n (85.4%) (Canada only). US strains resistant to ofloxacin were confir med by reference laboratory tests. Confirmed ofloxacin resistance, oth er than among staphylococci or nonenteric bacilli, was rare. The speci es most often found to be resistant to both ofloxacin and ciprofloxaci n were methicillin-resistant staphylococci, Acinetobacter spp., and En terococcus spp. From these contributing US and Canadian laboratory stu dies, ofloxacin appears to have a balanced spectrum of potential clini cal use (91.8% susceptible aerobic isolates), particularly against Gra m-positive pathogens and some species resistant to ciprofloxacin. The combined overall isolate (12,241 isolates) rates of susceptibility for ciprofloxacin (four infection sites) and norfloxacin (UTI only) were 87.3% and 88.8%, respectively. Monitoring for increasing fluoroquinolo ne resistance should be considered, however, as greater use of drugs i n this class develops.