title: The killing of Helicobacter pylori by low-power laser light in the presence of a photosensitiser.
abstract: Helicobacter pylori is associated with various gastrointestinal disorders. Lethal photosensitisation was investigated as a possible technique for killing H. pylori which might offer a better alternative to antibiotics. The susceptibility of H. pylori to lethal photosensitisation was determined by mixing suspensions of H. pylori with various photosensitisers and plating out on blood agar before irradiation with low-power 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 and pre-irradiation time. Crystal violet and thionine were ineffective as sensitisers, but zones of inhibition appeared with methylene blue (MB), protoporphyrin IX (PPIX), haematoporphyrin derivative (HPD), toluidine blue O (TBO) and disulphonated aluminium phthalocyanine (S2). Laser light or sensitiser alone did not affect bacterial viability. S2 (100 microg/ml) with a laser light energy density of 16 J/cm2, HPD (10O microg/ml) with 160 J/cm2, MB (100 microg/ml) with 21 J/cm2, PPIX (150 microg/ml) with 320 J/cm2 and TBO (50 microg/ml) with 160 J/cm2 all reduced bacterial viability by >99%. The killing of sensitised H. pylori by laser light offers a new approach to the treatment of localised infections when all colonised areas are accessible to light.
authors.affiliation: The National Medical Laser Centre, University College London Medical School, UK.
authors.forename: C E
authors.initials: CE
authors.lastname: Millson
authors.forename: M
authors.initials: M
authors.lastname: Wilson
authors.forename: A J
authors.initials: AJ
authors.lastname: Macrobert
authors.forename: J
authors.initials: J
authors.lastname: Bedwell
authors.forename: S G
authors.initials: SG
authors.lastname: Bown
mesh_terms: D004396:Coloring Agents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005840:Gentian Violet / Q000494:pharmacology; D016480:Helicobacter pylori / Q000187:drug effects / Q000528:radiation effects*; D017324:Hematoporphyrin Derivative / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D007834:Lasers; D008751:Methylene Blue / Q000494:pharmacology; D009942:Organometallic Compounds / Q000494:pharmacology; D010640:Phenothiazines / Q000494:pharmacology; D017319:Photosensitizing Agents / Q000494:pharmacology*; D011524:Protoporphyrins / Q000494:pharmacology; D014048:Tolonium Chloride / Q000494:pharmacology
chemical_list: D004396:Coloring Agents; D007211:Indoles; D009942:Organometallic Compounds; D010640:Phenothiazines; D017319:Photosensitizing Agents; D011524:Protoporphyrins; D014048:Tolonium Chloride; C060570:aluminum phthalocyanine; D017324:Hematoporphyrin Derivative; C028025:protoporphyrin IX; D005840:Gentian Violet; D008751:Methylene Blue; C009469:thionine