Killing of cutaneous microbial species by photodynamic therapy.
BACKGROUND
Photodynamic therapy (PDT) utilizes photosensitizers and light. Whereas PDT use in cancer treatment has been widely accepted, antimicrobial PDT (APDT) is still in its early stages of development.


OBJECTIVE
To study microbial killing in vitro using APDT.


METHODS
We used a combination of methylene blue and visible light, and a range of microbial species representative of those encountered on the skin in health and disease. Using standard light intensity conditions (slide projector, 25 cm distance from target, 42 mW cm(-2)) and methylene blue dye at 100 microg mL(-1), kill rates and subsequent D-values were determined against Staphylococcus aureus, S. epidermidis, Streptococcus pyogenes, Corynebacterium minutissimum, Propionibacterium acnes and Candida albicans.


RESULTS
D-values for these species were 72, 66, 48, 120, 30 and 660 s, respectively. The effects of light intensity on the killing of S. epidermidis showed the kill rate to be proportional to the light intensity. A high rate of cell kill was also obtained using natural sunlight.


CONCLUSIONS
Overall, these results indicate that APDT of the skin may represent a useful alternative to conventional antimicrobial treatment.
Zeina
B
B
Dermatology Department of Teshreen Hospital, Damascus, Syria.
Greenman
J
J
Purcell
W M
WM
Das
B
B
D001419:Bacteria / Q000187:drug effects* / Q000528:radiation effects; D002176:Candida albicans / Q000187:drug effects* / Q000528:radiation effects; D006801:Humans; D066298:In Vitro Techniques; D008751:Methylene Blue / Q000494:pharmacology; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000494:pharmacology; D012867:Skin / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000187:drug effects / Q000528:radiation effects; D013212:Staphylococcus epidermidis / Q000187:drug effects / Q000528:radiation effects
D017319:Photosensitizing Agents; D008751:Methylene Blue