The susceptibility to antibiotics, the relative expression level of MDR efflux pumps and target sites mutations of the spontaneous mutants.

Notes: CIP, ciprofloxacin; NOR, norfloxacin; OFX, ofloxacin; SAR, sarafloxacin; ENR, enrofloxacin; NAL, nalidixic acid; TET, tetracycline; CHL, chloramphenicol; FLO, florfenicol; ND, not tested; No, no mutatation; ST, Salmonella Typhimurium (CVCC541); SI1-SI4, the spontaneous mutants derived from ST under the selection pressure of ciprofloxacin; SR, SI1R, SI2R and SI3R, the mutant of ST, SI1, SI2 and SI3 with inactivated ramA, respectively; STRA and SI2RA, SR and SI1R with the overproduction of RamA, respectively; SI1RR, SI1 with the overproduction of RamR.