In vitro activities of new fluoroquinolones against Campylobacter jejuni and Campylobacter coli isolates obtained from humans in 1980 to 1982 and 1997 to 2001.

The antibacterial activities of three newly developed fluoroquinolones (gatifloxacin, levofloxacin, and moxifloxacin) against a total of 307 gastrointestinal human isolates of Campylobacter jejuni and Campylobacter coli collected during 1980 to 1982 and 1997 to 2001 were examined and compared to those of ciprofloxacin and the unrelated antibacterial agents, clarithromycin, erythromycin, and tetracycline by using the agar plate dilution method. All of the fluoroquinolones exhibited a good activity against Campylobacter, and some of them were more active than ciprofloxacin, the macrolides, and tetracycline. Among the fluoroquinolones, gatifloxacin and moxifloxacin showed the highest anticampylobacter activity, with MICs at which 50% of the isolates tested are inhibited (MIC(50)s) and MIC(90)s of 0.125 and 4 microg/ml, respectively; the MIC(50) for both levofloxacin and ciprofloxacin was 0.25, and the MIC(90)s were 16 and 32 microg/ml, respectively. About 30% of the strains were found to be resistant to at least one fluoroquinolone. Resistance to gatifloxacin occurred in 9.8% of the isolates tested, and resistance to the other fluoroquinolones occurred in 19.9 to 27.4% of the isolates tested; the frequency of cross-resistance was 35.7 to 100%. An increase in fluoroquinolone resistance from 0% in 1980 to 1982 to 11.8 to 29% in 1997 and 1998, 8.2 to 31.8% in 1999 and 2000, and 12.1 to 30.3% in 2001 was found. A total of 61.4 to 73.2% of the C. jenuni strains resistant to erythromycin, clarithromycin, and/or tetracycline were susceptible to fluoroquinolones; gatifloxacin showed the highest percentage of inhibition. These results show that the newer fluoroquinolones with their potent activity could be used to treat infections with C. jejuni and C. coli. However, when these drugs are used, one must consider the increase in resistance and the high cross-resistance to these antimicrobial agents.