Fig. 1
MNQ extensively potentiates tetracyclines activity. a The screening scheme of candidate compounds in the current study. The effective synergists against tet(X4)-positive E. coli were derived from 28 quinones using the broth micro-dilution method. bāc MNQ effectively synergized with tetracycline antibiotics (including tetracycline, tigecycline, oxytetracycline, methacycline, minocycline) against E. coli DH5Ī±ā+āpAM401-tet(X3) (b) and E. coli DH5Ī±ā+āpAM401-tet(X4) (c) by chequerboard broth microdilution assays. Dark regions represent higher cell density. d MNQ restored the susceptibility of multiple tetracyclines against tet(X4)-carrying E. coli J53p47EC. The experiments were repeated at least three times independently. FIC index ā¤0.50 was defined as synergism