An efflux inhibitor of the MacAB pump in Salmonella enterica serovar Typhimurium

Multidrug efflux pumps play an important role in bacterial multidrug resistance by actively excreting antibiotics. The ATP‐binding cassette–type drug efflux pump MacAB was originally reported as a macrolide‐specific pump. MacAB is also known to be required for the virulence of Salmonella enterica serovar Typhimurium following oral infection in mice. Here, we performed a screening of inhibitors of Salmonella MacAB and found a compound that increased the susceptibility of a MacAB‐expressing strain to macrolides. It was previously reported that MacAB is required to resist peroxide‐mediated killing in vitro and that a supernatant of wild‐type Salmonella rescues the growth defect of a macAB mutant in H 2 O 2 . In this study, we also found that the MacAB inhibitor reduced the ability of the supernatant to rescue Salmonella cells in H 2 O 2 . This compound could lead to a better understanding of the function of MacAB.