#$%^&*AU2018204190A120180705.pdf#####C: Intrwoven NRPortbI DCC KZill 7144503l.docx-12 06/2018 ABSTRACT Compositions and methods, including novel homogeneous microparticulate suspensions, are described for treating natural surfaces that contain bacterial biofilm, including unexpected synergy or enhancing effects between bismuth-thiol (BT) compounds and certain antibiotics, to provide formulations including antiseptic formulations. Previously unpredicted antibacterial properties and anti-biofilm properties of disclosed BT compounds and BT compound-plusantibiotic combinations are also described, including preferential efficacies of certain such compositions for treating certain gram-positive bacterial infections, and distinct preferential efficacies of certain such compositions for treating certain gram-negative bacterial infections.