Percentages (%) of biofilm-biomasses of Escherichia coli after treatment with (A) HAMA-ERY and (B) GA-AMP combinations. In each test group, biomasses of “Total biofilm” were thought to be 100%, and with this consideration the percent (%) biomasses of dead (Propidium Iodide-stained) biofilm and live (SYTO9-stained) biofilm were calculated. Data were analyzed by one-way analysis of variance with F-test. Data represented as mean ± standard deviation of three (n = 3) independent experiments. * Represents significance difference (P < 0.05) among the effects of individual drugs and combination drugs within each concentration group. ** Represents significance difference (P < 0.05) compared with the untreated control group. AMP, ampicillin; ERY, erythromycin; GA, gallic acid; HAMA, hamamelitannin; MIC, minimum inhibitory concentration.