Evaluation of six fluoroquinolones for their capabilities in restricting the selection of resistant salmonellae

of a fluoroquinolone. 4,5 The MICs of the six fluoroquinolones for the strains tested (shown to be clonally unrelated by PFGE) are shown in Table 1. All were highly susceptible to the six fluoroquinolones tested with MICs as much as 64-fold lower than the susceptible breakpoints recommended by the CLSI 6 or the BSAC. 4 However, when the strains were subcultured in the presence of a fluoroquinolone, resistant strains developed at 1·–32· MIC at a frequency ranging from10 –11 to10 –6 .Gemifloxacincouldselectresistantstrainsatthe highest frequencies (10 –10 –1 0 –6 ), indicating that both Salmonella