Antimicrobial photodynamic therapy for the decolonization of methicillin-resistant Staphylococcus aureus from the anterior nares
2009
The nosocomial infection rate has increased dramatically due to emergence of antibiotic resistant bacterial strains such as
methicillin resistant Staphylococcus aureus (MRSA). The primary anatomical site of MRSA colonization is the anterior
nares, and this reservoir represents a primary vector of transmission from non-infected carriers to susceptible individuals.
Antimicrobial photodynamic therapy (aPDT) has been used successfully for topical disinfection in the oral cavity. The
aim of this study was to evaluate the utility of aPDT for nasal MRSA decolonization at the preclinical and clinical level.
The nasal aPDT system consists of a 670 nm diode laser fibre-optically coupled to a disposable light diffusing tip, used
to activate a methylene blue based photosensitizer formulation. Preclinical testing was done both in a custom nasal
reservoir model and on human skin cultures colonized on the epithelial surface with MRSA. Human clinical testing was
performed by clinicians in regions in which the system is approved by the regulatory authority. In vitro testing
demonstrated that aPDT eradicated planktonic MRSA in an energy 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. In preliminary human testing, aPDT eradicated MRSA completely from the
nose with total treatment times <10 minutes. aPDT is effective against MRSA when used topically in the nose. Energy
dose and photosensitizer parameters have been optimized for the nasal environment. Controlled clinical studies are
currently underway to further evaluate safety and efficacy.
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