Compositions and methods including novel homogeneous microparticulate suspensions are described for treating natural and artificial 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 plus antibiotic 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.
