Synergistic effect of photodynamic therapy at 400 nm and doxycycline against Helicobacter pylori

Aims: The objective of this study was to investigate the possible synergy between doxycycline and photodynamic therapy (PDT) against Helicobacter pylori and to evaluate the possible side effects on gastric cells (AGS cell line) with and without protoporphyrin IX. Materials & Methods: Three H. pylori strains (ATCC 700392, 43504 and 49503), were grown on solid medium either containing or not doxycycline at sub-inhibitory concentrations, and irradiated for 10, 20 and 30 minutes with a 400 nm-peaked light source. The phototoxicity tests on AGS cells was evaluated by MTT assay. Results : The PDT and doxycycline combination showed an antibacterial synergistic effect with no significant toxicities. Conclusions: The synergistic treatment could be considered as an interesting therapeutic option.