Effects of HAMA-ERY combination (A) and GA-AMP combination (B) on planktonic cells of Escherichia coli ATCC25922. Effects of HAMA-ERY combination (C) and GA-AMP combination (D) on biofilm cells of Escherichia coli ATCC25922. 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 drug 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.