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Photobactericidal activity of methylene blue derivatives against vancomycin-resistant Enterococcus spp
M Wainwright1, D A Phoenix, M Gaskell
1Photochemotherapy Group, Department of Biological Sciences, University of Central Lancashire, Preston PR1 2HE, UK. Public Health Laboratory, Royal Preston Hospital, Preston PR2 4HT, UK. m.wainwright@uclan.ac.uk
Abstract:
The toxicities and phototoxicities of methylene blue and its two methylated derivatives were measured against one standard and three vancomycin-resistant pathogenic strains of Enterococcus spp. Each of the compounds was bactericidal and the derivatives exhibited photobactericidal activity on illumination at a 'light' dose of 6.3 J/cm(2) against one or more of the strains. Increased bactericidal and photobactericidal activity in the methylated derivatives is thought to be due to their higher hydrophobicities allowing greater interaction with the bacterial cell wall. In addition, the derivatives exhibited higher inherent photosensitizing efficacies.