Aerosolized Hydrogen Peroxide May Counter MRSA Environmental Contamination

Bob Roehr

September 18, 2007 (Chicago) — Aerosolized hydrogen peroxide demonstrates an excellent ability to neutralize methicillin-resistant Staphylococcus aureus (MRSA) environmental contamination, according to a new study. The neutralization appears to approach 100% and to last for weeks. It holds the promise of cost-effective infection control.
The key study, presented here yesterday at the 47th Interscience Conference on Antimicrobial Agents and Chemotherapy, was conducted at the Royal Hampshire County Hospital, Winchester, in the United Kingdom. In January 2007, a previously "clean" 28-bed surgical ward suffered an unexpected outbreak of MRSA in which 11 patients quickly became colonized.
Rotating sections of the ward were closed, and traditional decontamination cleaning took place. Moistened cotton swabs were used to gather samples from 29 standardized sites both before and after the hydrogen peroxide treatment and then at 1-week intervals for 4 weeks. Patients were screened at admission and discharge, and the staff was also screened; anyone found positive for MRSA was decolonized successfully.
The study found MRSA at 8 (27.6%) of 29 sites after traditional cleaning but at 1 (3.4%) of 29 sites after hydrogen peroxide treatment. The sites remained negative for MRSA on 3 successive weekly examinations, but on week 4, MRSA could be detected at 3 (10.3%) of 29 sites.
Study coauthor Jonathan Otter, PhD(c), works for Bioquell Ltd, the company that is developing commercial application of the technology, and participated in the study along with the hospital and government health agencies.
Mr. Otter believes that managing environmental contamination — in which the source of an infection has no direct physical contact with the patient who becomes infected but instead deposits the pathogen on a surface for third-party transmission — is an underappreciated part of infection control.
Mr. Otter explained that the decontamination process uses 30% hydrogen peroxide and a hot plate to create the vapor. Over the course of about 2 hours, the H2O2 settles on all exposed surfaces, and the highly reactive molecule destroys the pathogen. The reaction is not specific to MRSA, but that was the only pathogen measured in this study.
"In a previously presented study, a hospital in Connecticut instituted this technology for a period of 10 months throughout the entire facility, with a 53% reduction in colonization," Mr. Otter said.
He was not prepared to discuss cost of the decontamination process but said that a regularly provided service would be cheaper and more cost-effective than a single, small intervention. In addition, although institutional settings are the first priority, he believes that it will be a cost-effective technology for use in small medical practices where there is reason to believe there may be MRSA contamination.
Earlier research has shown that dust and organic matter can create a shield that provides some protection to the pathogen from exposure to H2O2 vapor, so prior cleaning is advised. However, Mr. Otter said that even without precleaning, the process seems to kill about 90% of MRSA.
The work in England has focused on hospital-acquired MRSA in part because community-acquired (CA)-MRSA occurs at much lower levels than have been seen recently in the United States. Molecular analysis in the Winchester study identified 5 different genetic sequences of MRSA. The process worked against all of them, and given its mechanism of action, there is no reason to believe that the procedure will not work equally well against CA-MRSA.
Although anterior nares is the most sensitive site for detecting MRSA colonization, 2 other studies presented at the conferences demonstrated that it is not the only place one should be looking.
A study of 72 residents of extended care units within the Veterans Administration Maryland Health Care System compared colonization of USA300 and non-USA300 MRSA. It found 48 (67%) of 72 residents with a history of MRSA to be colonized; 41 residents (85%) had a positive anterior nares culture.
However, the rates of colonization differed by genotype. Among residents colonized with USA300 MRSA, 14 (78%) of 18 residents were colonized in the anterior nares compared with 27 (90%) of 30 residents with non-USA300 MRSA colonized in the anterior nares. The rates of skin colonization did not differ by genotype; 56% (10 of 18) for USA300 and 57% (17 of 30) for non-USA300 MRSA.
Dominik Mertz, MD, working at the University Hospital Basel in Switzerland, found that a quarter of carriers of MRSA were colonized in the throat and not in the nares. Using multivariate analysis, he also found that young age and lack of regular interface with the healthcare system were associated with carriage in the throat. Dr. Mertz could offer no explanation as to why.
The Westminster study activities were funded jointly by Bioquell, the Royal Hospital, and the National Health Service. Dr. Otter is employed by Bioquell. Dr. Mertz reported no relevant financial relationships.
47th Interscience Conference on Antimicrobial Agents and Chemotherapy: Abstracts K-464, K-448, K-449. Presented September 17, 2007.