Figure 3.

Expected and observed inhibitory effects of combined treatment of mature biofilms with antibiotic (ampicillin or ciprofloxacin) and 64 g/L OligoG. Inhibitory effects are expressed as percent change in viable cells (log₁₀ cfu/mL) compared with no-treatment control. Expected effects (dashed lines) were calculated using the Bliss independence approach (see text for formula) with mean inhibitory effects by individual treatments (three technical replicates) as input. Observed inhibitory effects (full lines) were calculated separately for each of the three technical replicates, with subsequent calculation of means and determination of 95% CI (assuming Student’s t-distribution to account for low sample size). Significant synergism was defined as ‘observed effect (lower 95% CI) > expected effect’ while significant antagonism was defined as ‘observed effect (upper 95% CI) < expected effect’. Significant synergism or antagonism is indicated by asterisks above or below 95% CI, respectively. Vertical lines indicate MBIC (dashed), MB2LDC (dotted/dashed) and BBC by combined treatment (Table 2). Axis scales are harmonized for easier comparison.