Comparison of in vitro photodynamic antimicrobial activity of protoporphyrin IX between endoscopic white light and newly developed narrowband endoscopic light against Helicobacter pylori 26695

Helicobacter pylori might be readily affected with photodynamic therapy (PDT) by weak wavelengths, because it has few repair genes. Recently, gastrointestinal endoscopy emitting specific wavelengths (narrowband imaging, NBI) has been developed for the early detection of tumors. Coincidentally, its wavelength (415 nm) is very similar to the wavelength (410 nm) that activates protoporphyrin IX (PpIX) as a photosensitizer (PS). Therefore, we studied in vitro PDT against H. pylori using NBI and conventional white light (WL) according to low or high concentration of PpIX along with exposure time. The bactericidal effects, the degree of oxidative DNA damage and membrane integrity of H. pylori after PDT were evaluated. In the control, the numbers of viable cells remained constant during the experiment. Viable cells after PDT using both endoscopic light irradiation, were decreased approximately 103 – 105 fold at low concentration of PpIX and below 0.80 × 10 at high concentration of PpIX. Only membrane damage after PDT was observed microscopically in H. pylori without DNA injury. Conclusively, either the bactericidal effect in high concentration or the decrease of bacterial loading in low concentration of PpIX, would be expected with PDT using endoscopic light (NBI or WL).

► We undertook a study, for the first time, whether endoscopic narrow band light has bactericidal effects like WL on H. pylori.
► Viable cells after PDT using both endoscopic light irradiation, were decreased approximately 103 – 105 fold at 0.002% to 0.005% and below 0.80 × 10 at 0.02% of PpIX.
► The bactericidal activities of PDT using PpIX with both WL and NBI light sources are very effective and the major mechanism of PDT involves cell membrane injury.