<i>Aeromonas salmonicida</i>: development of resistance to 4‐quinolone antimicrobials

Abstract

Abstract. This paper examines aspects of the resistance of Aeromonas salmonicida isolates to the major fish farming antimicrobials. The antimicrobial resistance of an extensive chronological series of isolates appears to reflect the changing use of different compounds in fish farming since 1969. Repetitive challenge by 50% MIC concentrations of 4‐quinolone antimicrobials against selective isolation of viable colonies resulted in a 7·2 × increase in resistance in 12 generations, demonstrating the likely outcome of drug misuse.