Hydrogen peroxide vapor kills MRSA, other environmental pathogens

November 1, 2007

Hydrogen peroxide vapor has demonstrated an excellent ability to eradicate methicillin-resistant Staphylococcus aureus (MRSA) environmental contamination, according to a poster presented at the 47th Annual Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) in Chicago in September.

Key Points

The study was conducted at the Royal Hampshire County Hospital, Winchester, England, in January 2007. A previously "clean" 28-bed surgical ward experienced an outbreak of MRSA in which 11 patients quickly became colonized with the pathogen.

Sections of the ward were closed on a rotating basis and decontaminated using the vapor process. Cotton swabs were used to gather samples from 29 standardized sites both before and after the hydrogen peroxide (H2O2) treatment and then at one-week intervals for four weeks. Patients were screened at admission and discharge, and the staff also were screened; anyone found positive for MRSA was decolonized successfully.

None of the patients admitted to the ward in the four-week period following the intervention acquired MRSA, so the outbreak response was successful. However, because the hospital used multiple interventions, it is not possible to say which intervention was most effective.

Jon Otter, a Ph.D. candidate in microbiology who is focusing on MRSA, works for BIOQUELL (U.K.) Ltd., the British company that is developing commercial application of the technology. He played a leading role in this and other studies.

Sorting out the proportions of transfer attributed to each route is a difficult task, and primarily of academic interest, as effective infection control should address all risk factors for infection.

Mr. Otter tells Dermatology Times that the decontamination process "creates the vapor from 30 percent hydrogen peroxide." The proprietary technology ensures even distribution of the vapor. "During the exposure period, a 'micro-condensation' of H2O2 forms on all exposed surfaces. A typical cycle in a single room takes about two hours from start to finish."

The exact mechanism of action in killing the pathogen has not yet been fully characterized - and likely varies from bug to bug - but, given what is known of H2O2, it likely involves hydroxyl radicals that attack multiple cellular targets of the pathogen.

The reaction is not specific to MRSA; BIOQUELL has demonstrated similar efficacy against a variety of stubborn pathogens. Efficacy was seen in a decontamination study of Mycobacterium tuberculosis at a research laboratory at the Mayo Clinic in Rochester, Minn., and a study of Clostridium difficile at a Connecticut hospital, where the rate of infection was cut in half over a 10-month period.

Earlier research has shown that dust and organic matter can create a shield that provides some protection to the pathogen from exposure to the vapor, so prior cleaning is advised. However, Mr. Otter says that even without pre-cleaning, "The process seems to kill about 90 percent of MRSA."