Sugar N-formyltransferase that catalyzes the conversion of dTDP-4-amino-4,6-dideoxyglucose into dTDP-4-formamido-4,6-dideoxyglucose using N(10)-formyltetrahydrofolate as the carbon source. Plays a role in virulence. (6S)-10-formyltetrahydrofolate + dTDP-4-amino-4,6-dideoxy-alpha-D-glucose = (6S)-5,6,7,8-tetrahydrofolate + dTDP-4-formamido-4,6-dideoxy-alpha-D-glucose + H(+) Homodimer. Belongs to the dTDP-Qui4N formyltransferase family.