In vitro activity of gemifloxacin and other antimicrobial agents against isolates of Bordetella pertussis and Bordetella parapertussis

We investigated the activity of the novel quinolone agent gemifloxacin (SB- 265805) and a panel of comparator agents against Bordetella pertussis and B ordetella parapertussis. Erythromycin, azithromycin, ciprofloxacin and gemi floxacin were consistently active against both species. An azithromycin- an d erythromycin-resistant B. pertussis isolate was not resistant to any of t he other agents tested (gemifloxacin MIC less than or equal to 0.008 mg/L; ciprofloxacin,,less than or equal to 0.015 mg/L; ampicillin, 2.0 mg/L; trim ethoprim-sulphamethoxazole, 4.0 mg/L). The potency of ampicillin, azithromy cin, erythromycin, ciprofloxacin and trimethoprim-sulphamethoxazole recorde d against B. pertussis and B. parapertussis in this study was comparable to that noted in previous studies. However, MICs were generally higher than t hose noted in other trials; this may reflect the different methods used. Al though in vitro data on the potency of gemifloxacin against B. pertussis an d B. parapertussis have not previously been reported, these results are com parable to the potency of other quinolones against these pathogens. Should gemifloxacin achieve similar concentrations within the respiratory tract as other quinolones, this, coupled with its high in vitro potency, suggests t hat gemifloxacin has potential clinical efficacy in pertussis.