Comparison of the methylene blue and toluidine blue photobactericidal efficacy against gram-positive and gram-negative microorganisms

Marina N. Usacheva, Matthew C. Teichert, Merrill A. Biel

Research output: Contribution to journalArticlepeer-review

261 Scopus citations

Abstract

Background and Objective: Studies on the photobactericidal efficacy of methylene blue (MB) and toluidine blue (TB) have shown inconsistent results in the literature. This study evaluated the bactericidal efficacy of MB and TB against different bacteria under light and dark conditions to determine the most effective bactericidal dye. Study Design/Materials and Methods: Suspensions of Staphylococcus aureus, Streptococcus pneumoniae, Enterococcus faecalis, Hemophilus influenzae, Escherichia coli, and Pseudomonas aeruginosa in saline were treated in dark and red laser light conditions in the presence of each dye using an argon pumped-dye and a diode laser emitting light at 630 and 664 nm, respectively. The effect of dye concentration, dark incubation time, the fluence and intensity of laser light on the destruction of different bacteria were compared. Results: Both dyes eradicated all examined bacteria under laser light. The complete photodestruction of microorganisms was reached at TB concentrations of 1.5-7-fold less than that of MB. Conclusion: TB exhibits a greater bactericidal activity than MB against most bacteria in dark and light conditions. Mostly, these results are consistent with their respective dye partition coefficients.

Original languageEnglish (US)
Pages (from-to)165-173
Number of pages9
JournalLasers in Surgery and Medicine
Volume29
Issue number2
DOIs
StatePublished - Sep 12 2001

Keywords

  • Bacterial damage
  • Dark toxicity
  • Low-power red lasers
  • Pathogenic microorganisms
  • Phenothiazine dyes
  • Photodynamic therapy
  • Photosensitizers

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