Figure 6: The antibacterial effect of quaternary ammonium salts of pyridoxine against biofilm-embedded S. aureus and S. epidermidis cells. Bacteria were grown for 72 h to form a rigid biofilm. Next the medium was replaced by the fresh one after double washing to remove nonadherent cells; compounds were added as indicated followed by 24 h incubation. Afterwards the number of viable cells was evaluated by staining the cells with propidium iodide and acridine orange. The estimated percentage of nonviable cells is given in the lower right corner of each panel. Magnification ×63.