A significant percentage of the population (30-40%) are asymptomatic carriers of S. aureus, and 1%-5% of individuals in the community are colonized with MRSA. In hospitals, the percentage of people colonized with MRSA can be much higher, with some studies suggesting rates as high as 10%. While the bacteria can be found on various parts of the body, the primary anatomical site of colonization is the anterior (forward) nasal passages. Furthermore, the nose represents a primary vector of transmission from non-infected carriers to themselves, other patients, and healthcare workers. In fact, most MRSA infections arise from an endogenous source, and nasal carriage has been found to increase the risk of infection by almost 4-fold.
Decolonization therapy for carriers of S. aureus/MRSA has been proposed as a measure to reduce transmission and decrease overall infection rates. Several clinical studies have provided evidence that decolonization of the nose and other body sites can lead to a decrease in healthcare-associated infection rates, and this has led to the commercialization of rapid screening assays for nasal MRSA detection. However, current decolonization procedures have not been widely adopted because of the cost associated with isolation during treatment and the potential for an increase in antibiotic resistance. There exists a clinically unmet need for a rapid, effective, non-antibiotic therapy to achieve decolonization in confirmed carriers before transmission can occur within your hospital
MRSAid™ Nasal Decolonization
Current MRSA decolonization procedures vary widely, but usually consist of some combination of disinfectant body wash, topical antibiotic for nasal clearance (e.g. mupirocin), and systemic antibiotic therapy. While these methods can be effective, the widespread use of antibiotics is often associated with a growing incidence of antibiotic resistance. Furthermore, topical antibiotics require a treatment course of five or more days to be effective, raising issues of patient compliance and potential communicability over the course of therapy. The MRSAid™ system is designed to work as part of a broad infection control and decolonization protocol. It may be used adjunctively with or in replacement of topical nasal antibiotics, and offers the distinct advantages of:
- absence of development of bacterial resistance to the killing mechanism of aPDT,
- elimination of patient compliance issues with a multi-day treatment schedule, and
- immediate and powerful nasal decolonization of pathogens.
Scientific and Clinical Results
Preclinical testing of the MRSAid™ system for safety and efficacy has been peer-reviewed and presented at international conferences in the areas of photodynamics and infection control. These studies demonstrated that the system is effective in eradication of both S. aureus and MRSA under optimized photosensitizer and energy dose conditions. Furthermore, testing on epithelialized human skin cultures demonstrated the ability to eliminate established topical colonization of MRSA. Histopathological assessment of these treated skin samples showed that treatment with MRSAid™ does not induce cell/tissue damage.
Because of the generalized mechanism of bacterial membrane destruction inherent to Photodisinfection, it is unlikely that bacteria can develop resistance to this treatment in the same way they do to traditional antibiotics. In a controlled laboratory study, antibiotic sensitive and resistant strains of S. aureus were subjected to repeat Photodisinfection treatments. Treatment parameters were adjusted such that kills were <100% so that surviving bacterial colonies could be propagated for subsequent exposures. With each repeat, antibacterial activity was compared to those using virgin, non-exposed cultures of the same strain. Over a total of 25 repeat exposures to Photodisinfection, no significant difference in killing (vs. virgin cultures) was observed using either strain of S. aureus. In contrast, complete oxacillin resistance could be generated in S. aureus after 10-12 repeat exposures. This work demonstrated that Photodisinfection is effective against S. aureus, regardless of whether the strain exhibits prior antibiotic resistance. Furthermore, repeated sub-lethal exposure to Photodisinfection does not induce resistance to subsequent PDT treatments. The absence of resistance formation represents a significant advantage of PDT over traditional antibiotics.
Clinical testing using MRSAid™ has shown that the system effectively decolonizes the nasal passages of confirmed MRSA carriers. An early case series, using several treatment protocols, showed elimination of nasal MRSA carriage in 17 of 19 subjects. More recent testing in a Canadian MRSA clinic also showed that nasal decolonization could be achieved with a single application of MRSAid™ and that decolonization was maintained over multiple days post-treatment. These promising results have supported the design of larger clinical studies to be performed at key infection control centers across Canada.