Phototherapy Shows Success in Battling MRSA

Terry Stanton

A program aimed at reducing surgical site infections (SSIs) using intranasal antimicrobial photodynamic therapy resulted in partial or complete nasal decolonization in up to 82 percent of cases of Staphylococcus aureus infection.

These results, recorded at Vancouver General Hospital in Canada over a 1-year study period, represent not only a high rate of success but were achieved using a simple, confirmable same-day photodynamic application combined with the patient washing with 2 percent chlorhexidine body wipes the day before.

Phototherapy is a promising form of microbial eradication, noted presenter Bas A. Masri, MD, FRCSC, because it is not subject to drug resistance and can be delivered rapidly with minimal adverse events. Variations on this technology have been used successfully in other medical fields, including oncology and dentistry.

Dr. Masri explained that for effective application, three components must be present: a photosensitizer, light, and oxygen. The light energy is typically supplied by an external source such as a laser, with a wavelength matched to the absorption/emission properties of the photosensitizer, which results in the creation of bactericidal oxygen free radicals.

Phototherapy has the advantage of being a horizontal decolonization strategy in that it is active against gram-positive and -negative bacteria in addition to viruses and fungi. It is targeted to the tissues that the user selects with the photosensitizer; the photosensitizer does not bind to human tissue, and the light produces minimal heat with no evidence of thermal damage.

“Traditional methods use an antibiotic ointment twice daily for 5 days to reduce the bacterial burden in the nose,” said Dr. Masri. “Photodynamic therapy allows immediate bacterial kill following a single application while the patient is in the perioperative care center just before surgery. This will improve compliance and make it much easier for patients. This will also allow the surgeon to know that the patient has received appropriate treatment just before surgery.”

SSIs represent a significant cost burden and resource diversion for hospitals, resulting in increased patient length of stay, morbidity, and mortality. Of special concern are infections with antibiotic-resistant strains such as methicillin-resistant S. aureus (MRSA). Presurgical bundles using mupirocin ointment and chlorhexidine can reduce the risk, but such strategies are disadvantaged by poor compliance, lengthy treatment time, and increasing resistance to antibiotics, the authors report.

Up to 30 percent of patients may be colonized with S. aureus at any time; their risk of having related infections develop is three to six times greater than noncarriers. In most cases, the S. aureus colonization is caused by the patient’s endogenous flora, with the nose as a major vector.

Patients in this study had a methicillin-sensitive S. aureus (MSSA) nasal colonization rate of 23.4 percent and an MRSA nasal colonization rate of 1.0 percent. Although some studies have shown no benefit from nasal decolonization, current consensus is to apply it in high-risk surgical procedures, the authors write.

New protocol established
In June 2011, the hospital adopted the photodynamic protocol, which was implemented across all surgical specialties over the next 3 months. Data collection for this study began in September and lasted 12 months.

The 5,627 patients in the study received nonemergency cardiac, orthopaedic trauma, orthopaedic reconstruction, spine thoracic, vascular, breast, and neurosurgical procedures. As part of the preoperative visit, patients were instructed to wash with non-alcohol–based 2 percent chlorhexidine body wipes within 24 hours before surgery, using a different washcloth for each limb, the front of the torso, and the back of the torso.

On the day of surgery, patients received intranasal photodynamic therapy while waiting in the perioperative area. Nasal culture swabs were obtained immediately prior to and after therapy. Microbiologic efficacy was determined by comparing the degree of intranasal S. aureus colonization before and after phototherapy.

Overall, photodynamic therapy was successful in 81.7 percent of the patients with MSSA and 76.4 percent of those with MRSA.

Dr. Masri noted that the therapy has some potential disadvantages, including a higher initial set-up cost, training necessary to perform the treatments, and integration of the technique in the perioperative area. In this study, he noted that the degree of compliance was high and patients were accepting. There was a low adverse event rate (0.12 percent), consisting of seven instances of mild and transient irritation in the back of the throat, probably related to trickling of methylene blue solution.

Dr. Masri’s coauthors for Scientific Presentation 481, “Nasal Decolonization of Staphylococcus aureus with Antimicrobial Photodynamic Therapy” were Elizabeth Bryce, DMed; Titus Wong, MD; Diane Roscoe, MD; Cale Street, PhD, MBA; Deborah Jeske, RN, MA; Shelagh Weatherill, RN, MA; and Leslie Forrester, MSc.

Disclosure information: Dr. Bryce—Online Biomedical; Dr. Roscoe—College of American Pathologists; Dr. Street—Online Biomedical; Dr. Masri—Techniques in Knee Surgery, Journal of Arthroplasty, Canadian Orthopaedic Association, AAOS; Ms. Weatherill—Online Biomedical. Dr. Wong and Ms. Jeske reported no conflicts; no data available for Ms. Forrester.

2013 Annual Meeting News
Tuesday through Friday, February 19 – 23, 2013.
http://www.aaos.org/news/acadnews/2013/AAOS11_3_22.asp