553. Nasal Decolonization of Methicillin-Resistant Staphylococcus aureus using antimicrobial photodynamic therapy
Session: Poster Abstract Session: MRSA Surveillance and Infection Prevention
Friday, October 21, 2011
Room: Poster Hall B1
  • 553_RachelAnderson.pdf (467.2 kB)
  • Background: A significant percentage of the population (30-40%) are carriers of Staphylococcus aureus, and up to 10% are colonized with an antibiotic resistant form of the organism known as MRSA. While this bacteria can live anywhere on the skin, the primary site of long-term colonization is the anterior nasal passages. Nasal decolonization therapy is emerging as a viable approach to reduce pathogen transmission and decrease overall infection rate in the hospital setting. Antimicrobial photodynamic therapy (aPDT) is a non-antibiotic broad spectrum antibacterial technology that may be useful for topical disinfection of MRSA in the nose.

    Methods: aPDT, using a 670 nm non thermal diode laser to activate a methylene blue based photosensitizer formulation, was evaluated in two preclinical models. A custom nasal reservoir in vitro model was used to optimize exposure parameters (photosensitizer concentration, light exposure), and a MRSA-colonized human epithelial skin culture model was used to evaluate decolonization potential and effects on tissues. Subsequent human nasal decolonization testing was performed on confirmed MRSA carriers (n=11) in a clinical setting.

    Results: In vitro testing demonstrated that aPDT eradicated MRSA cultures in a light dose and photosensitizer concentration dependent manner. Furthermore, aPDT eliminated sustained colonization of MRSA on cultured human epithelial surfaces, an effect that was sustained over multiple days post-treatment. Histopathological analysis of treated full thickness tissue samples showed no change in structure or cellular morphology compared to non-treated controls. Nasal decolonization testing in humans showed that colonized individuals could be rendered MRSA negative with total treatment times <15 minutes.

    Conclusion: aPDT was found to be effective against S. aureus/MRSA at the preclinical level without causing damage to human tissues. Human testing also showed that aPDT can achieve full nasal decolonization of these pathogens with relatively short treatment times. Larger clinical studies are currently underway to assess efficacy and impact on hospital infection rate.

    Subject Category: N. Hospital-acquired and surgical infections, infection control, and health outcomes including general public health and health services research

    Cale Street, PhD, MBA1, Lisa Pedigo, BS1, Aaron Gibbs, BS1, Roger Andersen, MD1, Nicolas Loebel, PhD1, Merrill Biel, MD, PhD2 and Thomas Louie, M D3, (1)Ondine Research Laboratories, Bothell, WA, (2)Photobiologix Inc, Minneapolis, MN, (3)University of Calgary, Calgary, AB, Canada


    C. Street, Ondine Biomedical Inc: Employee, Salary

    L. Pedigo, Ondine Biomedical Inc: Employee, Salary

    A. Gibbs, Ondine Biomedical Inc: Employee, Salary

    R. Andersen, Ondine Biomedical Inc: Employee, Salary

    N. Loebel, Ondine Biomedical Inc: Employee, Salary

    M. Biel, Ondine Biomedical Inc: Board Member, Collaborator, Consultant and Shareholder, Consulting fee

    T. Louie, Ondine Biomedical Inc: Collaborator, Medical equipment for conducting clinical testing

    Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.