title: Inactivation of Vibrio parahaemolyticus by antimicrobial photodynamic technology using methylene blue.
abstract: BACKGROUND
  Vibrio parahaemolyticus is the leading causative pathogen of gastroenteritis often related to contaminated seafood. Photodynamic inactivation has been recently proposed as a strategy for killing cells and viruses. The objective of this study was to verify the bactericidal effects caused by photodynamic inactivation using methylene blue (MB) over V. parahaemolyticus via flow cytometry, agarose gel electrophoresis and sodium dodecyl sulfate polyacrylamide gel electrophoresis. Vibrio parahaemolyticus counts were determined using the most probable number method. A scanning electron microscope and a transmission electron microscope were employed to intuitively analyze internal and external cell structure.
  
  
  RESULTS
  Combination of MB and laser treatment significantly inhibited the growth of V. parahaemolyticus. The inactivation rate of V. parahaemolyticus was >99.99% and its counts were reduced by 5 log10 in the presence of 0.05 mg mL(-1) MB when illuminated with visible light (power density 200 mW cm(-2)) for 25 min. All inactivated cells showed morphological changes, leakage of cytoplasm and degradation of protein and DNA.
  
  
  CONCLUSIONS
  Results from this study indicated that photodynamic technology using MB produced significant inactivation of V. parahaemolyticus mainly brought about by the degradation of protein and DNA.
authors.affiliation: Department of Food Science and Engineering, Jinan University, Guangzhou, 510632, China.
authors.forename: Xi
authors.initials: X
authors.lastname: Deng
authors.affiliation: Department of Food Science and Engineering, Jinan University, Guangzhou, 510632, China.
authors.forename: Shuze
authors.initials: S
authors.lastname: Tang
authors.affiliation: Department of Food Science and Engineering, Jinan University, Guangzhou, 510632, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Wu
authors.affiliation: Department of Food Science, South China Agricultural University, Guangzhou, 510642, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Tian
authors.affiliation: Department of Food Science and Engineering, Jinan University, Guangzhou, 510632, China.
authors.forename: William W
authors.initials: WW
authors.lastname: Riley
authors.affiliation: Department of Photoelectrical Engineering, Jinan University, Guangzhou, 510632, China.
authors.forename: Zhenqiang
authors.initials: Z
authors.lastname: Chen
mesh_terms: D001426:Bacterial Proteins; D004249:DNA Damage / Q000187:drug effects / Q000528:radiation effects; D004269:DNA, Bacterial / Q000187:drug effects / Q000528:radiation effects; D005516:Food Microbiology; D059022:Food Safety; D008027:Light; D008751:Methylene Blue; D050296:Microbial Viability / Q000187:drug effects / Q000528:radiation effects; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D017319:Photosensitizing Agents; D017747:Seafood / Q000382:microbiology; D014736:Vibrio parahaemolyticus / Q000187:drug effects* / Q000528:radiation effects*; D014871:Water Microbiology
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D017319:Photosensitizing Agents; D008751:Methylene Blue
keywords: Vibrio parahaemolyticus; antimicrobial photodynamic inactivation; methylene blue; photodynamic mechanism