Figure 2. Frequencies of emergence of spontaneous FQ^R mutants in different C. jejuni strains including the wild-type 11168, the mfd mutant (JH01), the complemented mfd mutant (JH02), and the mfd-overexpressing construct (JH03).

Three different concentrations of CIPRO (1, 2, and 4 µg/ml, respectively) were used in the detection plates to count FQ^R colonies. Each bar represents the mean±standard deviation of frequencies from three independent cultures. The bars labeled with different letters indicate that they are significantly different (P<0.05).