Activity of a dry mist hydrogen peroxide system against environmental Clostridium difficile contamination in elderly care wards

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Summary

Clostridium difficile causes serious healthcare-associated infections. Infection control is difficult, due in part to environmental contamination with C. difficile spores. These spores are relatively resistant to cleaning and disinfection. The activity of a dry mist hydrogen peroxide decontamination system (Sterinis®) against environmental C. difficile contamination was assessed in three elderly care wards. Initial sampling for C. difficile was performed in 16 rooms across a variety of wards and specialties, using Brazier's CCEY (cycloserine–cefoxitin–egg yolk) agar. Ten rooms for elderly patients (eight isolation and two sluice rooms) were then resampled following dry mist hydrogen peroxide decontamination. Representative isolates of C. difficile were typed by polymerase chain reaction ribotyping. C. difficile was recovered from 3%, 11% and 26% of samples from low, medium and high risk rooms, respectively. In 10 high risk elderly care rooms, 24% (48/203) of samples were positive for C. difficile, with a mean of 6.8 colony-forming units (cfu) per 10 samples prior to hydrogen peroxide decontamination. Ribotyping identified the presence of the three main UK epidemic strains (ribotypes 001, 027 and 106) and four rooms contained mixed strains. After a single cycle of hydrogen peroxide decontamination, only 3% (7/203) of samples were positive (P < 0.001), with a mean of 0.4 cfu per 10 samples (∼94% reduction). The Sterinis® hydrogen peroxide system significantly reduced the extent of environmental contamination with C. difficile in these elderly care rooms. This relatively quick and user-friendly technology might be a more reliable method of terminally disinfecting isolation rooms, following detergent cleaning, compared to the manual application of other disinfectants.

Introduction

Clostridium difficile infection is endemic in most UK hospitals. Symptoms range from self-limiting diarrhoea, to potentially life-threatening pseudomembranous colitis. The financial cost has been estimated to be at least £4,000 per case equating to £400,000 per year and the loss of 21 000 bed-days for an average-sized general hospital.1, 2

Despite efforts to improve hand hygiene and to restrict antibiotic use, there is increased concern over the number and severity of C. difficile infections, particularly following the emergence of the hypervirulent ribotype O27 (NAP-1).3 The environment is often overlooked as a potential source of hospital-acquired infection and C. difficile spores can remain viable for several weeks, resisting drying, detergents and some chemical disinfectants.4, 5, 6, 7, 8, 9 There is a positive correlation between C. difficile in the environment and its prevalence on the hands of healthcare workers.10 Reducing the environmental reservoir of C. difficile may reduce the risk of transmission but some previous attempts to improve cleaning methods have failed to reduce infection rates.5, 9, 11, 12

Current guidelines recommend the use of chlorine-based disinfectants or other sporicidal products to disinfect bed spaces and rooms previously occupied by patients with C. difficile, and there is some evidence to suggest that chlorine-based disinfectants are more effective than ordinary detergents at reducing environmental contamination.9, 13 However, in a clinical setting it can be difficult to ensure the correct concentrations of disinfectant solutions, complete application of liquid disinfectants to all contaminated surfaces and equipment and adequate disinfectant contact times. UK hospitals operate at bed occupancies often >95% and so time constraints are an obstacle to effective terminal cleaning.14 Inadequate manual cleaning and disinfection may actually increase sporulation, distributing C. difficile over a wider area.15

There is increasing interest in the use of hydrogen peroxide delivery systems as an alternative to manual terminal disinfection. The BioQuell® system has been shown to be more effective than manual cleaning for removing environmental contamination with meticillin-resistant Staphylococcus aureus (MRSA) in single rooms and has been used as part of control measures for outbreaks of both MRSA and C. difficile.4, 16, 17, 18 In one US hospital affected by the epidemic NAP-1 strain of C. difficile, hydrogen peroxide vapour (HPV) was shown to significantly reduce the environmental recovery of C. difficile and a 10-month programme of HPV decontamination was associated with a 39% reduction in new cases of infection.19

The Sterinis® system is an alternative hydrogen peroxide delivery system which uses a dry mist of 5% hydrogen peroxide with traces of silver cations (<50 ppm) and orthophosphoric acid (<50 ppm). The dry mist of small particles (8–12 μm) ensures homogeneous diffusion throughout the room and maximises contact with potentially contaminated surfaces. The gaseous nature of this broad-spectrum disinfectant increases penetration to inaccessible areas such as radiator grilles and is non-toxic, non-corrosive, electrically safe and 99.99% biodegradable, with the hydrogen peroxide breaking down to minimal amounts of water and oxygen within 2 h of deployment.

The aim of this study was to assess the levels of C. difficile environmental contamination in a variety of clinical areas and to evaluate the activity of the Sterinis® dry mist hydrogen peroxide system against environmental C. difficile in contaminated rooms.

Section snippets

Accommodation

A three-month ward-based study was carried out at the City Campus, Nottingham University Hospital, UK in 2006. Environmental samples were collected from clinical areas deemed high, moderate and low risk, based on local C. difficile infection rates. These included: 11 rooms across three high risk elderly care wards (nine isolation rooms and two utility/sluice rooms), two isolation rooms on a haematology unit (moderate risk) and an isolation room in each of one obstetric, paediatric and elective

Results

C. difficile was isolated from at least one sample in all but one of the rooms studied. However, there was a clear difference in the extent of C. difficile contamination between the low, medium and high risk areas (Table I).

Hydrogen peroxide dry mist decontamination was used in 10 rooms on the elderly care wards. The sampling results before and after decontamination are also shown in Table I. C. difficile was recovered from all 10 rooms before decontamination but from only five rooms following

Discussion

In this study we found that all nine elderly patient isolation rooms were contaminated with the current UK epidemic strains of C. difficile. These rooms were sampled after they had been cleaned, including some rooms that had been cleaned and then terminally disinfected with 1% hypochlorite. This suggests that the routine manual cleaning and disinfection does not reliably remove environmental C. difficile. In contrast, using the same sampling methodology, we found very low levels of

Acknowledgements

We thank J.S. Brazier for supplying ribotyping standard strains and advice regarding culture media.

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    Further standards are due to be published shortly (see https://standardsdevelopment.bsigroup.com/projects/2019-00332#/section). Because automated room decontamination devices are designed to be used alongside traditional (manual) cleaning/disinfection methods, the levels of microbiological environmental contamination present are unlikely to exceed 105 micro-organisms on a given surface area [94–97]. Some overseas authorities require hospital disinfectants to achieve at least a 6 log10 reduction of certain vegetative bacteria in vitro.

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This work was presented in part at the Federation of Infection Societies meeting, Cardiff, UK, November 2007.

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