Investigation into the potential of sub-lethal photodynamic antimicrobial chemotherapy (PACT) to reduce susceptibility of meticillin-resistant Staphylococcus aureus (MRSA) to antibiotics

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

In PACT, a combination of a sensitising drug and visible light cause the selective destruction of microbial cells via singlet oxygen production. As singlet oxygen is a non-specific oxidizing agent and is only present during illumination, development of resistance to this treatment is thought to be unlikely. However, in response to oxidative stress, bacteria can up-regulate oxidative stress genes and associated antibiotic resistance genes. The up-regulation of these genes and potential transfer of genetic material may result in a resistant bacterial population. This study determined whether treatment of clinically isolated meticillin resistant Staphylococcus aureus (MRSA) strains with sub-lethal doses of methylene blue (MB) and meso-tetra (N-methyl-4-pyridyl) porphine tetra tosylate (TMP)-PACT resulted in reduced susceptibility to antibiotics and previously lethal PACT. Exposure of strains to sub-lethal doses of photosensitizer in combination with light had no effect on susceptibility to previously lethal photosensitization. Furthermore, exposure to sub-lethal concentrations of both photosensitizers caused no significant changes in the minimum inhibitory concentration (MIC) for each strain tested. Any differences in susceptibility were not significant as they did not cross breakpoints between resistant and susceptible for any organism or antibiotic tested. Therefore, PACT remains an attractive alternative option for treatment of MRSA infections.

Original languageEnglish
Title of host publication12th World Congress of the International Photodynamic Association - Photodynamic Therapy
Subtitle of host publicationBack to the Future
DOIs
Publication statusPublished - 01 Dec 2009
Event12th World Congress of the International Photodynamic Association - Photodynamic Therapy: Back to the Future - Seattle, WA, United States
Duration: 11 Jun 200915 Jun 2009

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
Volume7380
ISSN (Print)1605-7422

Conference

Conference12th World Congress of the International Photodynamic Association - Photodynamic Therapy: Back to the Future
Country/TerritoryUnited States
CitySeattle, WA
Period11/06/200915/06/2009

Keywords

  • antibiotic
  • methylene
  • MRSA
  • photodynamic
  • resistance

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Atomic and Molecular Physics, and Optics
  • Radiology Nuclear Medicine and imaging

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