ANTIMICROBIAL ACTIVITY OF MEROCYANINE-540 - A PHOTOSENSITIZING DYE

The antimicrobial activity of merocyanine 540 (MC 540), a photosensiti zing dye previously used to purge malignant cells from autologous bone marrow grafts, was evaluated against a panel of Gram-positive and Gra m-negative bacteria and Candida albicans in the presence and absence o f light. In the absence of light, MC 540 demonstrated no antibacterial activity against any of the organisms tested. When combined with incr easing intervals of photoillumination, growth inhibition was observed with all Gram-positive organisms tested except Mycobacterium fortuitum . Photosensitizing growth inhibition was also observed with Moraxella catarrhalis but not with any other Gram-negative bacilli including mem bers of the Enterobacteriaceae, Pseudomonas aeruginosa, Acinetobacter baumannii, Stenotrophomonas maltophila, or Burkhoderia cepacia. These results suggested that differences in cell wall structure confer resis tance to the photodamaging effects of the dye. MC 540 exhibited no ant imicrobial activity against C. albicans in the presence of absence of light. (C) 1998 Elsevier Science Inc.