THE KILLING OF HELICOBACTER-PYLORI BY LOW-POWER LASER-LIGHT IN THE PRESENCE OF A PHOTOSENSITIZER

Helicobacter pylori is associated with various gastrointestinal disord ers, Lethal photosensitisation was investigated as a possible techniqu e for killing H. pylori which might offer a better alternative to anti biotics, The susceptibility of H. pylori to lethal photosensitisation was determined by mixing suspensions of H. pylori with various photose nsitisers and plating out on blood agar before irradiation with low-po wer laser light, Five sensitisers were studied further by mixing them with H. pylori in a tissue-culture plate and counting survivors after irradiation as a function of laser exposure time, dye concentration an d pre-irradiation time, Crystal violet and thionin were ineffective as sensitisers, but zones of inhibition appeared with methylene blue (MB ), protoporphyrin IX (PPIX), haematoporphyrin derivative (HPD), toluid ine blue O (TBO) and disulphonated aluminium phthalocyanine (S2), Lase r light or sensitiser alone did not affect bacterial viability, S2 (10 0 mu g/ml) with a laser light energy density of 16 J/cm(2), HPD (100 m u g/ml) with 160 J/cm(2), MB (100 mu g/ml) with 21 J/cm(2), PPIX (150 mu g/ml) with 320 J/cm(2) and TBO (50 mu g/ml) with 160 J/cm(2) all re duced bacterial viability by > 99%, The killing of sensitised H. pylor i by laser light offers a new approach to the treatment of localised i nfections when all colonised areas are accessible to light.