Fig. 3

Biofilm antimicrobial activity: metabolic activity with XTT. In the presence of metabolically active S. mutans biofilms (i.e., no antimicrobial compound added), XTT is continuously converted to a strongly absorbing formazan derivative until depleted (a). Using the XTT assay response (at 45 min) to evaluate CPC antimicrobial activity against 24 h biofilms (b), a similar response was observed for manual (bottom) and automated (top) assays. Grey lines in b connect n = 4 replicates for each [CPC]; black traces, points, and horizontal bars in b show three-factor logistic fits, calculated IC50 values, and day-to-day precision, as described in the “Materials and methods” section