In vitro activities of 11 fluoroquinolones against 226 Campylobacter jejuni strains isolated from Finnish patients, with special reference to ciprofloxacin resistance

Abstract

Although Campylobacter jejuni is naturally susceptible to fluoroquinolones, the resistance to these antimicrobials has increased rapidly during the recent years. The aim of this study was to compare the activities of various older and newer fluoroquinolones towards C. jejuni, with special attention on ciprofloxacin-resistant strains. We analysed the in vitro activities of 11 fluoroquinolones against 226 C. jejuni strains collected from Finnish patients between 1995 and 2000. Of all 226 C. jejuni strains, 134 (59.3%) were resistant to ciprofloxacin (MIC > or = 4 mg/L), 1 (0.4%) was intermediately resistant (MIC = 2 mg/L) and 91 (40.3%) were ciprofloxacin-susceptible (MIC < or = 1 mg/L). The MIC50 and MIC90 values of ciprofloxacin for the 91 ciprofloxacin-susceptible strains were 0.25 and 0.5 mg/L, respectively. The corresponding MIC50 and MIC90 values of levofloxacin were 0.25 and 0.5 mg/L, and those of moxifloxacin were 0.125 and 0.25 mg/L, these being lower than those of norfloxacin and ofloxacin. The two newer fluoroquinolones, sitafloxacin and clinafloxacin, exhibited the lowest MIC50 and MIC90 values: 0.016 and 0.064 mg/L of sitafloxacin and 0.032 and 0.125 mg/L of clinafloxacin, respectively. Sitafloxacin and clinafloxacin exhibited the lowest MIC50 and MIC90 values also for the 134 ciprofloxacin-resistant C. jejuni strains: 0.25 and 1 mg/L of sitafloxacin and 1 and 4 mg/L of clinafloxacin, respectively. Of the newer fluoroquinolones presently under development, sitafloxacin is in vitro highly effective towards C. jejuni, with low MIC values also for the ciprofloxacin-resistant strains. Sitafloxacin might be a candidate for clinical trials on campylobacteriosis.