PHOTODYNAMIC EFFECTS OF DEUTEROPORPHYRIN ON GRAM-POSITIVE BACTERIA

The photodynamic effects of deuteroporphyrin (DT) on the growth and viability of Staphylococcus aureus, Streptococcus faecalis, and Bacillus cereus are described. By exposure to light and DT, the growth of Sta. aureus and Str. Faecalis strains was markedly inhibited, whereas B. cereus was undergoing lysis. Counting the viable bacteria during the DT treatment revealed that more than 99% of the initial bacterial population was killed within the first 30 min of treatment. The pH dependence of the photodynamic inhibitory effect shows that it is best obtained at pH 6.5. No temperature dependence in the range of 37°-44°C could be detected. The best photodynamic effect was achieved when the culture was in the mid-log phase. DT-treated bacteria, when grown in the dark or in the presence of horse serum albumin, were unaffected by the porphyrin action. Electron microscopic examinations of Sta. aureus and Str. faecalis showed the appearance of well-developed mesosomes within the cell cytoplasm. B. cereus preparations have not shown any mesosome formation but showed some lysed cells as well as some spores. None of the mentioned effects by DT and light could be observed on Gramnegative bacteria such as Escherchia coli or Pseudomonas aeruginosa. © 1987 Springer-Verlag New York Inc.