title: Inactivation of Staphylococcus aureus by photodynamic action of hypocrellin B.
abstract: OBJECTIVE
  Staphylococcus aureus is a common opportunistic pathogen causing human infections. In the present study, we investigated photodynamic inactivation on S. aureus using hypocrellin B from a traditional Chinese herb.
  
  
  METHODS
  After incubation of S. aureus cells with different concentrations of hypocrellin B for 60 min, subsequent light irradiation from a novel LED light source with wavelength of 470 nm was combined with the energy density of 0.3 J/cm(2). Phototoxicity of hypocrellin B on S. aureus was investigated by colony forming unit assay. Membrane permeability was measured using confocal laser scanning microscopy (CLSM) with propidium iodide (PI) staining. Intracellular reactive oxygen species (ROS) level was measured using flow cytometry (FCM) with DCFH-DA staining. Morphology and structure of treated and controlled bacteria were observed using transmission electron microscopy (TEM).
  
  
  RESULTS
  Activity of S. aureus was substantially inhibited by photodynamic action in hypocrellin B dose-dependent manner. Notable damage to S. aureus were found in TEM after photodynamic treatment of hypocellin B. Red fluorescence of PI dye was observed more frequently in bacterial cells treated by photodynamic action of hypocrellin B than those of bacterial cells treated by the controls including sham control, hypocrellin B treatment alone and light irradiation alone. Intracellular ROS increase was also found in S. aureus treated by photodynamic action of hypocrellin B.
  
  
  CONCLUSIONS
  Photodynamic action of hypocrellin B markedly increased intracellular ROS level and caused damage to membrane permeability, resulting in cell death of S. aureus.
authors.affiliation: Department of Rehabilitation Medicine, First Affiliated Hospital of Chengdu Medical College, Sichuan, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Jiang
authors.forename: Albert Wingnang
authors.initials: AW
authors.lastname: Leung
authors.forename: Xinna
authors.initials: X
authors.lastname: Wang
authors.forename: Hongwei
authors.initials: H
authors.lastname: Zhang
authors.forename: Chuanshan
authors.initials: C
authors.lastname: Xu
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D004203:Disinfection / Q000379:methods*; D004305:Dose-Response Relationship, Drug; D010569:Perylene / Q000008:administration & dosage / Q000031:analogs & derivatives*; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000008:administration & dosage; D011809:Quinones / Q000008:administration & dosage*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000502:physiology* / Q000528:radiation effects
chemical_list: D017319:Photosensitizing Agents; D011809:Quinones; D010569:Perylene; C064522:hypocrellin B
keywords: Hypocrellin B; Light-emitting diode; Photodynamic inactivation; Staphylococcus aureus