In vitro activities of oxolonic acid, ciprofloxacin and norfloxacin against Aeromonas salmonicida

Abstract. Oxolinic acid and two new fluoroquinolones, ciprofloxacin and norfloxacin, were evaluated for in vitro antibacterial activity against Aeromonas salmonicida. Although oxolinic acid was as active as ciprofloxacin in terms of minimum inhibitory concentration (MIC), fluoroquinolones were significantly more active in terms of their ability to kill both oxolinic acid sensitive and resistant strains of A. salmonicida. Furthermore, the fluorinated drugs were active against non‐dividing A. salmonicida. It would appear worthwhile to carry out further investigations with fluoroquinolones as they may be more effective in treating A. salmonicida infections than the current regime of oxolinic acid.