Maximum metabolic rate of treated and untreated (control) P. aeruginosa PAO1 biofilms. (A) MA: 60 mM d,l-malic acid; CIP: 1.2 μg/ml ciprofloxacin; MA-CIP: 60 mM d,l-malic acid combined with 1.2 μg/ml ciprofloxacin. (B) SA: 120 mM sodium acetate; CAZ: 12.48 μg/ml ceftazidime; SA-CAZ: combination of 120 mM sodium acetate and 12.48 μg/ml ceftazidime. Values shown are the mean (n ≥ 3). Error bars indicate standard error, **, P < 0.01; ***, P < 0.001.