part_of regulates protein(s) and two-component regulatory system modulating antibiotic efflux MexEF-OprN MexS PA2491 MexS is a suppressor of MexT, which is an activator of the multidrug pump MexEF-OprN. Mutations in MexS lead to multidrug resistance. ARO:3000813 qrh antibiotic_resistance nfxC MexS MexEF-OprN with MexS mutations conferring resistance to chloramphenicol, ciprofloxacin, and trimethoprim