Fig. 5

Antimicrobial activity screening. Automated methods facilitated the screening of antimicrobial activity against S. mutans. Planktonic (left), biofilm forming (center), and 24 h biofilm (right) growth conditions were evaluated for the antimicrobial activity of three halide salts (Cl⁻, Br⁻, I⁻) of the cetylpyridinium cation (labeled CPC, CPB, and CPI, respectively). Culture growth was assessed by turbidity and metabolic activity, as discussed for Fig. 4. Grey lines connect n = 4 replicates for each [CPC]; black traces, points, and horizontal bars show three-factor logistic fits, calculated IC50 values, and day-to-day precision, as described in the “Materials and methods” section. All antimicrobial concentrations were plotted as molarities to facilitate comparisons between compounds (molecular weights are listed in the “Materials and methods” section)