INACTIVATION OF ANAEROBIC-BACTERIA BY VARIOUS PHOTOSENSITIZED PORPHYRINS OR BY HEMIN

The photodynamic effects of deuteroporphyrin (DP), hematoporphyrin der ivative (HPD), hematoporphyrin (HP), or protoporphyrin (PP) on a varie ty of anaerobic microorganisms were examined in this study. The majori ty of the species, among the 350 strains tested, were inhibited by con centrations of less than or equal to 2.5 mu g/ml of light-activated DP . Species found to be resistant to this treatment included Bilophila w adsworthia, Fusobacterium mortiferum, Fusobacterium varium, and Bacter oides gracilis. These species were inhibited by concentrations of > 60 mu g/ml of DP. The porphyrin-producing species, Porphyromonas and Pre votella spp, were all inhibited by less than or equal to 2.5 mu g/ml D P and light. Comparing the photodynamic activity of the porphyrins use d on Porphyromonas strains resulted in the following pattern: DP > HPD > HP > PP. Porphyromonas spp., Gram-positive cocci, and many Gram-pos itive rods (excluding clostridia) were inactivated by hemin (a metal-c ontaining porphyrin) at 10-20 mu g/ml. Hemin inhibitory action was not : affected by light. Binding and insertion of DP into bacteria (both i nactivated and non-inactivated strains by DP and light) were monitored by the characteristic fluorescence band of bound DP at 622 nm. Porphy romonas spp. bound DP tightly, whereas only low binding was seen with B. wadsworthia and other DP-resistant species. High binding of DP to B . wadsworthia can be achieved by pretreatment of the bacteria with imi penem or cefoxitin, beta-lactam agents known to interfere with the int egrity of the cell wall. If cell wall integrity is disturbed (e.g., by these agents), inactivation of B. wadsworthia by DP can occur.