Energy-dependent efflux mediated by class L (tetL) tetracycline resistance determinant from streptococci.

The class L (TetL) tetracycline resistance determinant from streptococci specified resistance and an energy-dependent decreased accumulation of tetracycline in both Streptococcus faecalis and Escherichia coli. Using E. coli, we showed that the reduced uptake resulted from active efflux. The streptococcal class M determinant, known to render the protein synthesis machinery of S. faecalis resistant to tetracycline inhibition, did not alter tetracycline transport in either host.