Figure 6. Effect of PIP and RES on the efficacy of antibiotics (A) ciprofloxacin (CIP 5 µg/mL) and (B) azithromycin (ATH 15 µg/mL) towards fully developed E. coli CFT073 biofilms.

The biofilms were allowed to form for 48 h and were subsequently incubated with the alkaloids for 24 h. Control indicates biofilms not treated with antibiotic or alkaloids. All biofilm values (OD₅₇₀) are normalized with growth (OD₆₀₀). Values for OD₅₇₀ are presented in Figure S6. Abbreviations: PIP 0.5 or RES 0.5, piperine or reserpine at 0.5 µg/mL (e.g., PIP 0.5 indicates piperine at 0.5 µg/mL). * indicates statistically significant (p<0.05) decrease in biofilm level for alkaloid + antibiotic treatment compared to the respective antibiotic treatment (CIP 5 or ATH 15).