Inactivation of staphylococcal virulence factors using a light-activated antimicrobial agent.
BACKGROUND
One of the limitations of antibiotic therapy is that even after successful killing of the infecting microorganism, virulence factors may still be present and cause significant damage to the host. Light-activated antimicrobials show potential for the treatment of topical infections; therefore if these agents can also inactivate microbial virulence factors, this would represent an advantage over conventional antibiotic therapy. Staphylococcus aureus produces a wide range of virulence factors that contribute to its success as a pathogen by facilitating colonisation and destruction of host tissues.


RESULTS
In this study, the ability of the light-activated antimicrobial agent methylene blue in combination with laser light of 665 nm to inactivate staphylococcal virulence factors was assessed. A number of proteinaceous virulence factors were exposed to laser light in the presence of methylene blue and their biological activities re-determined. The activities of V8 protease, alpha-haemolysin and sphingomyelinase were shown to be inhibited in a dose-dependent manner by exposure to laser light in the presence of methylene blue.


CONCLUSIONS
These results suggest that photodynamic therapy could reduce the harmful impact of preformed virulence factors on the host.
Division of Microbial Diseases, UCL Eastman Dental Institute, UK. s.tubby@eastman.ucl.ac.uk
Sarah
S
Tubby
Michael
M
Wilson
Sean P
SP
Nair
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D005260:Female; D006358:Hot Temperature; D008027:Light; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects* / Q000528:radiation effects; D008751:Methylene Blue / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008826:Microbial Sensitivity Tests; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000494:pharmacology*; D013203:Staphylococcal Infections / Q000188:drug therapy; D013696:Temperature; D037521:Virulence Factors / Q000528:radiation effects*; D014946:Wound Infection / Q000188:drug therapy
D000900:Anti-Bacterial Agents; D017319:Photosensitizing Agents; D037521:Virulence Factors; D008751:Methylene Blue