Bile salts possess innate antibacterial properties and can cause significant damage to bacteria. To survive in the mammalian gut, has developed mechanisms to tolerate bile salts; however, the specific mechanisms remain unclear. Transposon library screening revealed that the efflux pump AcrAB is involved in bile salt resistance. and mutants exhibited high sensitivity not only to bile salts but also to SDS and various antibiotics, with a switch-loop, comprising residues G615, F616, A617, and G618, proving to be crucial in this process. A colonization defect of and mutants was demonstrated to be located in the mouse small intestine, where the bile salt concentration is higher compared to the large intestine. Additionally, both and mutants displayed reduced virulence in the model. In conclusion, our results suggest that the Resistance-Nodulation-Cell Division efflux pump serves as a critical determinant in the pathogenesis of through various aspects.