Effect of iron chelation on anti-pseudomonal activity of doxycycline

•High affinity iron chelation enhances the antibacterial activity of tetracyclines.•High affinity iron chelation synergises with doxycycline against P. aeruginosa.•Doxycycline chelates iron and loses antibacterial activity.•Iron chelation re-establishes the susceptibility of iron bound doxycycline.•Iron chelation enhances doxycycline activity in a biofilm setting.