title: Toluidine blue O photodynamic inactivation on multidrug-resistant Pseudomonas aeruginosa.
abstract: OBJECTIVE
  Multidrug-resistant (MDR) Pseudomonas aeruginosa infection is becoming a critical problem worldwide. Currently, only limited therapeutic options are available for the treatment of infections caused by MDR P. aeruginosa, therefore, the development of new alternative treatments is needed. Toluidine blue O (TBO) is an effective antibacterial photosensitizing agent against various bacteria. However, reports on antibacterial photosensitization of MDR bacteria are limited. This study aims to determine the in vitro photobactericidal activity of TBO against MDR P. aeruginosa.
  
  
  METHODS
  The efficacy of antibacterial photodynamic inactivation, DNA fragmentation and protein carbonylation of three MDR P. aeruginosa strains and one susceptible strain was compared using TBO as the photosensitizer followed by red light irradiation (630 nm, 90 J/cm(2)) from a light-emitting diode light source. Subsequently, the efficacy of TBO photodynamic inactivation (TBO-PDI) on 60 MDR strains, including 11 with the efflux pump phenotype and 49 with no pump activity, was tested using the minimum lethal drug concentration (MLC) assay.
  
  
  RESULTS
  TBO-PDI caused similar bactericidal effect (6-7 logs of killing effect), DNA fragmentation and protein carbonylation in three MDR and one susceptible P. aeruginosa strains. Although the TBO accumulation assay indicated that TBO is a substrate for the efflux pump, TBO-PDI produce similar photobactericidal activity against 60 MDR P. aeruginosa strains, either with or without efflux-pump phenotype, and 19 susceptible strains.
  
  
  CONCLUSIONS
  MDR did not affect the susceptibility of P. aeruginosa strains to TBO-PDI. The efflux pump played an insignificant role in TBO-PDI of MDR P. aeruginosa.
authors.affiliation: Department of Clinical Laboratory Sciences and Medical Biotechnology, National Taiwan University College of Medicine, Taipei, Taiwan.
authors.forename: S P
authors.initials: SP
authors.lastname: Tseng
authors.forename: L J
authors.initials: LJ
authors.lastname: Teng
authors.forename: C T
authors.initials: CT
authors.lastname: Chen
authors.forename: T H
authors.initials: TH
authors.lastname: Lo
authors.forename: W C
authors.initials: WC
authors.lastname: Hung
authors.forename: H J
authors.initials: HJ
authors.lastname: Chen
authors.forename: P R
authors.initials: PR
authors.lastname: Hsueh
authors.forename: J C
authors.initials: JC
authors.lastname: Tsai
mesh_terms: D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects* / Q000528:radiation effects*; D006801:Humans; D008826:Microbial Sensitivity Tests; D010778:Photochemotherapy; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000528:radiation effects*; D014048:Tolonium Chloride / Q000494:pharmacology*
chemical_list: D014048:Tolonium Chloride