Antibiofilm activity of N-acetylcysteine (NAC) at 8,000 mg/L, colistin (CST), and NAC-CST combinations against P. aeruginosa Z154 in the Nunc-TSP lid system. A relevant potentiation of colistin antibiofilm activity was observed with all NAC-CST combinations tested. CST 2, colistin at 2 mg/L; CST 4, colistin at 4 mg/L; CST 8, colistin at 8 mg/L. Biofilms not exposed to NAC or CST represent the control. Black lines indicate median values. The x axis is set at the limit of detection (20 CFU/peg).