Graphical representation of the results of checkerboard assays testing synergistic interactions between myricetin and two selected antibiotics (clarithromycin and metronidazole) against clinical, double-resistant H. pylori strains (clarithromycin- and metronidazole-resistant). The MIC of myricetin for all strains is equal to 160 µg/mL. The MICs for clarithromycin count for 8, 4, and 16 µg/mL for H. pylori M26, M91, and M145, respectively. The MICs for metronidazole are equal to 64, 64, and 256 µg/mL for H. pylori M26, M91, and M145, respectively. The blue field marks the wells of the titration plates, in which no bacterial growth and a positive interaction between the tested compounds was observed. The interactions were interpreted based on the calculation of the FICI, in which ≤0.5 and >0.5 but ≤1 was considered as synergism and additivity, respectively.