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 H2 O2 . In this study, we also found that the MacAB inhibitor reduced the ability of the supernatant to rescue Salmonella cells in H2 O2 . This compound could lead to a better understanding of the function of MacAB.