Vapour's role in decontamination

15th of September 2010
Vapour's role in decontamination
Vapour's role in decontamination

How significant is environmental contamination in the transmission of hospital infection? Jon Otter and Dr Saber Yezli from Bioquell address this issue and explain the company's hydrogen peroxide vapour technology.

Hospital infection is a substantial and increasing problem around the world. The global problems due to nosocomial infections are illustrated by the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) around the world, which accounts for more than half of S. aureus in many countries, and increasing rates of Clostridium difficile infection (CDI) in the USA, Europe and elsewhere.

Is environmental contamination in hospitals clinically relevant? A number of organisms that are often implicated in hospital-acquired infections (HAI) are known to contaminate the hospital environment. These include Gram-positive cocci such as MRSA and vancomycin-resistant enterococci (VRE); spore forming Gram-positive rods such as C. difficile;  Gram-negative rods including the Enterobacteriaceae, for example Klebsiella sp., Escherichia coli and Acinetobacter sp.; viruses such as Novovirus and fungi such as Aspergillus sp. There is increasing evidence that transfer of nosocomial pathogens via the contaminated environment is a significant route of transmission for certain micro-organisms.

Studies have demonstrated that vegetative nosocomial bacteria can survive for many months when dried onto surfaces. For example, MRSA and A. baumannii were found to survive in excess of 300 days on dry surfaces in one study. Other studies have shown that conventional cleaning does not always eradicate pathogens from surfaces.

Although direct transmission of nosocomial pathogens via healthcare workers hands is widely considered to be the most important route of transmission, healthcare workers hands can become contaminated indirectly through contact with the inanimate environment in clinical areas. This could represent a significant and underestimated route of transmission. Environmental contamination has been shown to be a significant factor in the transmission of several pathogens including C. difficile, VRE, MRSA and A. baumannii.

Hydrogen peroxide vapour (HPV) decontamination

HPV is a sporicidal vapour-phase method that is being used increasingly in hospitals and healthcare facilities. HPV has been used for more than 15 years in the life science and pharmaceutical industries for the provision of sterile manufacturing and research facilities, and has been used in hospitals for more than six years.

The process works by injecting HPV into a hospital room, bay or ward in order to inactivate pathogens on surfaces and equipment inside the enclosure. The system consists of two principle modules: the HPV generator, which converts 30 per cent w/w liquid hydrogen peroxide into HPV and distributes it around the enclosure and the aeration unit, which catalytically converts the HPV to oxygen and water vapour after the cycle. The process is controlled by a lectern mounted control panel situated outside the room.

The process to decontaminate a single room is as follows: following patient discharge, the room is cleaned to remove visible dirt or soiling. Then the HPV equipment is set up in the room, air vents and doors are sealed and smoke detectors are covered. The HPV decontamination cycle typically takes between one-and-a-half and two hours, depending on the size of the room. During the cycle, the operator periodically checks for leakage using a hand-held HPV sensor. The next patient can be admitted immediately after the cycle is completed.

HPV decontamination has several advantages over manual cleaning. Because HPV is a vapour-phase method, full surface sterilisation occurs inside the room. The system is controlled automatically by a computer so does not rely on the operator to achieve adequate, repeatable distribution. HPV is effective in vitro against a wide range of nosocomial pathogens including MRSA, VRE, A. baumannii and C. difficile spores, and cycles are validated using Geobacillus stearothermophilus biological indicators – the same challenge used to verify that autoclaves are functioning correctly. Also HPV is catalytically decomposed to oxygen and water vapour so it is effectively residue free and compatible with sensitive electronics.

Pilot implementations

A pilot implementation of HPV decontamination in a large London hospital demonstrated the in situ efficacy of HPV for the eradication of environmental MRSA.

Key findings

•Overall, 74 per cent of 359 swabs were positive for MRSA before intervention.
•MRSA found at high levels in clinical areas used to treat patients who were not MRSA positive (eg, 43 per cent of the bed frames of one ward).
•After conventional cleaning, 66 per cent of 124 swabs positive for MRSA.
•MRSA cultured from high-risk sites before and after cleaning, which could act as fomites for MRSA transmission such as bed frames, TV remotes and door handles.
•After Bioquell’s HPV, only one per cent of swabs found to have a low level of MRSA contamination.

The UK Department of Health/Health Protection Agency Rapid Review Panel (RRP) was established in response to recommendations in the chief medical officer’s 2003 Annual Report entitled ‘Winning Ways’.The remit of the RRP is to review technologies with potential to help in the prevention and control of hospital infections. Bioquell’s technology was one of the first technologies to be reviewed by the RRP and in 2007 the RRP issued a report to the Department of Health, placing Bioquell’s technology in the highest category.

The RRP made the following specific comments: "Basic research and development, validation and recent in use evaluations have shown benefits that should be available to NHS bodies to include as appropriate in their cleaning, hygiene or infection control protocols."

Bioquell’s technology was assessed by the UK government funded Showcase Hospitals Programme, which examined the pilot introduction of HPV into seven NHS hospitals and concluded that: "The Bioquell system did not cause undue disruption and was very popular - 99 per cent of staff would recommend it."

Applications of HPV technology

A number of in-use evaluations have now been completed in clinical settings. HPV has been used to control outbreaks of various hospital pathogens including MRSA and Gram-negative bacteria. Many other as yet unpublished outbreak interventions have occurred and the results have been encouraging. Recent studies have shown the routine use of HPV decontamination reduces patient acquisition of C.difficile and VRE. Also, the feasibility of routine HPV decontamination has been demonstrated in busy hospitals in the UK and in the USA.

The decisions about where and when to apply HPV will depend on several factors, including whether there is an outbreak, the target pathogen and the scope of the deployment (ie, hospital wide or focussed on a high-risk area such as an intensive care unit). Several different deployment modes are available from Bioquell:

•Equipment purchase. The Q-10 suite is available for purchase to be owned and operated by the hospital. Bioquell provides full training and support to ensure that hospital operatives are able to utilise the equipment safely and effectively.

•Proactive service. As an alternative to purchasing equipment and having its own trained staff, a hospital can choose to use Bioquell technicians to operate the HPV equipment, which can be owned by either the hospital or Bioquell.

•Scheduled service. Sometimes hospitals know which areas will require decontamination and can plan in advance, for example, commissioning decontamination of operating theatres.

•Emergency response. Bioquell can usually respond within 24 hours to ensure that environmental contamination does not contribute to the continuation of hospital outbreaks.


It seems that the importance of contamination of the hospital environment with nosocomial pathogens has been historically underestimated - evidence is accumulating that rapidly contaminated environmental surfaces are an important source of transmission for several nosocomial pathogens. Bioquell’s HPV technology has been shown to eradicate important environmental pathogens from environmental surfaces and clinical evaluations have demonstrated an impact on rates of infection in epidemic and endemic scenarios. The optimal deployment of HPV in each hospital will depend on the local situation and hospital-specific objectives.


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