Roles of TolC-dependent multidrug transporters of Escherichia coli in resistance to beta-lactams.

AcrAB exports some beta-lactam antibiotics in the periplasm out of cells via an outer-membrane channel, TolC. It has been reported that eight drug transporters in Escherichia coli cooperate with TolC. In this study, the roles of the drug exporters of E. coli in beta-lactam resistance were examined. We found that five of five resistance-nodulation-cell division-type drug exporters confer beta-lactam antibiotic resistance, while no other drug exporters confer any beta-lactam resistance even when they cooperate with TolC.