Inactivation of anaerobic bacteria by various photosensitized porphyrins or by hemin

Abstract

The photodynamic effects of deuteroporphyrin (DP), hematoporphyrin derivative (HPD), hematoporphyrin (HP), or protoporphyrin (PP) on a variety of anaerobic microorganisms were examined in this study. The majority of the species, among the 350 strains tested, were inhibited by concentrations of < or = 2.5 micrograms/ml of light-activated DP. Species found to be resistant to this treatment included Bilophila wadsworthia, Fusobacterium mortiferum, Fusobacterium varium, and Bacteroides gracilis. These species were inhibited by concentrations of > 60 micrograms/ml of DP. The porphyrin-producing species, Porphyromonas and Prevotella spp, were all inhibited by < or = 2.5 micrograms/ml DP and light. Comparing the photodynamic activity of the porphyrins used on Porphyromonas strains resulted in the following pattern: DP > HPD > HP > PP. Porphyromonas spp., Gram-positive cocci, and many Gram-positive rods (excluding clostridia) were inactivated by hemin (a metal-containing porphyrin) at 10-20 micrograms/ml. Hemin inhibitory action was not affected by light. Binding and insertion of DP into bacteria (both inactivated and non-inactivated strains by DP and light) were monitored by the characteristic fluorescence band of bound DP at 622 nm. Porphyromonas 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 imipenem or cefoxitin, beta-lactam agents known to interfere with the integrity of the cell wall. If cell wall integrity is disturbed (e.g., by these agents), inactivation of B. wadsworthia by DP can occur.

Overcoming the Heme Paradox: Heme Toxicity and Tolerance in Bacterial Pathogens

“…However, the utility of heme is inseparable from its toxic effects, and the degree of sensitivity to heme toxicity varies among bacteria. In general, Gram-positive bacteria are more sensitive to heme toxicity than are Gram-negative bacteria (78). Notable exceptions to this trend are the anaerobic Gram-positive Clostridium spp.…”

“…Notable exceptions to this trend are the anaerobic Gram-positive Clostridium spp. and Gram-negative Porphyromonas spp., of which about 40% and 94% of tested strains are sensitive to heme toxicity, respectively (78). The variation in heme sensitivity observed across bacteria suggests one of two possibilities.…”

Potential applications of porphyrins in photodynamic inactivation beyond the medical scope

“…The advantage of being a process without a specific cell target renders photodynamic inactivation (PDI) effective in the oxidation of different biomolecules with the consequent destruction of several cell types. In fact, this methodology has a broad spectrum of activity and, using the same PS, is able to destroy human cells [1], viruses [5], bacteria [6], molds [7], yeasts [8], protozoa [9], helminths [10] and insects [11].…”

The Role of Heme Binding by DNA-protective Protein from Starved Cells (Dps) in the Tolerance of Porphyromonas gingivalis to Heme Toxicity

“…Furthermore, the release of iron during heme degradation can cause oxidative damage by the production of hydroxyl radicals via the Fenton reaction (Fe 2ϩ ϩ H 2 O 2 3 Fe 3ϩ ϩ OH ⅐ ). Indeed, a number of organisms, including Staphylococcus aureus, have been reported to be sensitive to heme toxicity (12,13).…”