The prevalence of fluoroquinolone resistance among clinically significant respiratory tract isolates of Streptococcus pneumoniae in the United States and Canada--1997 results from the SENTRY Antimicrobial Surveillance Program.

As part of the SENTRY antimicrobial resistance surveillance program, a total of 1100 clinically significant respiratory tract isolates of Streptococcus pneumoniae were tested for susceptibility to six fluoroquinolone antimicrobial agents: ciprofloxacin, levofloxacin, gatifloxacin, grepafloxacin, sparfloxacin, and trovafloxacin. Isolates were obtained during the 5-month period, February to June, 1997 from 27 United States medical center laboratories and seven laboratories in Canadian health care institutions. All testing was performed in a single center. Of 1100 test strains, 3 (0.3%), all from different U.S. centers, were fluoroquinolone resistant. Among the remaining 1097 fluoroquinolone-susceptible isolates, the rank order of activity among the six agents tested in this study was grepafloxacin (modal MIC = 0.25 microgram/mL) = trovafloxacin (modal MIC = 0.25 microgram/mL) = sparfloxacin (0.25 microgram/mL) > gatifloxacin (0.5 microgram/mL) > levofloxacin (1 microgram/mL) = ciprofloxacin (1 microgram/mL). Fluoroquinolone resistance is currently uncommon among respiratory tract isolates of S. pneumoniae in North America, but there exist clear differences between the in vitro activities of different fluoroquinolones for this organism.