Bioquell covers hydrogen-peroxide decontamination

In recent years, room/area bio-decontamination systems based on hydrogen peroxide have emerged.

These have been shown to decontaminate hospital surfaces more effectively than conventional methods.

The technology can also be used as a key part of infection control 'bundles'.

This white paper explores two of these systems, providing an insight into the significant differences between the technologies.

There are two different types of hydrogen peroxide-based room or area decontamination systems available.

Some are based on hydrogen peroxide vapour (HPV) and others are based on aerosolised hydrogen peroxide (aHP).

The Bioquell HPV system vaporises 30-35 per cent w/w aqueous hydrogen peroxide solution and uses a high-velocity air stream to achieve homogenous three-dimensional surface coverage throughout a room or enclosure.

The vapour is delivered into an enclosure until the air becomes saturated and hydrogen peroxide begins to condense on surfaces, typically laying down a uniform micro-condensate layer of 2-6 microns.

Following the HPV exposure and inactivation of micro-organisms, an active aeration system catalyses the breakdown of HPV to oxygen and water vapour.

aHP systems produce a fine mist by aerosolising a solution containing a significantly lower concentration of hydrogen peroxide solution (typically 5-10 per cent w/w), less than 50ppm silver ions and other chemicals.

The resultant mist/fog comprises droplets, often charged, typically ranging from 8-12 microns in diameter, which are usually injected in a single direction.

This does not give rise to an even distribution of the active in the room.

Following exposure, the hydrogen peroxide mist is left to decompose 'naturally' back to oxygen and water vapour without any active aeration or catalytic conversion system.

The fundamental differences between these technologies, in terms of the disinfection efficacy and delivery methods, result in a different microbiological impact.

The Bioquell HPV system is an EPA registered sterilant and is sporicidal.

Bioquell technicians routinely use Geobacillus stearothermophilus biological indicators (BIs) to verify cycle efficacy to a six-log reduction in bioburden - the same challenge used to validate steam sterilisers.

This 'surface sterilisation' gives hospitals substantial statistical comfort that micro-organisms have been eradicated from fomite sites.

In vitro studies have shown that the Bioquell system achieves a six-log reduction in C difficile spores.

When examining aHP systems, the reduction was recorded at a four-log reduction.

In practice, this would leave a 100-fold greater microbial bioburden in the environment when comparing aHP to Bioquell's HPV technology.

In addition, a study of the Bioquell system showed complete eradication of C difficile.

This compares to two studies of an aHP system which have shown incomplete inactivation of C.

difficile, with one or more positive cultures collected from 20 per cent of 15 and 50 per cent of 10 rooms studied.

Bioquell HPV has demonstrated efficacy against a range of nosocomial pathogens, including MRSA, VRE, Acinetobacter baumannii and MS2 coliphage (a viral surrogate).

It is notable that the Gram-negative organisms (Acinetobacter, Klebsiella) and MRSA proved particularly resistant to HPV in one study, due to the activity of catalase.

At the time of writing this white paper, no detailed published efficacy data against catalase-positive Gram-negative organisms exist for aHP systems.

These use much lower hydrogen peroxide concentrations against these key pathogens and it is likely that their efficacy will be significantly reduced.

Hence, low peroxide concentration systems may struggle to inactivate Gram-negative micro-organisms.

Likewise no data exist regarding the activity of aHP systems against Norovirus and its surrogates.

Certain aHP manufacturers also claim that the silver ions in their solution provide residual inhibition of microbial growth, though there are no published data in the scientific literature to support this.

Practical considerations are important for ensuring the safety and feasibility of these systems in hospitals.

The Bioquell HPV system achieves homogeneous distribution as it is a vapour, is routinely validated to a sterilisation threshold using six-log spore BIs, achieves repeatable inactivation of micro-organisms and is controlled remotely.

Handheld sensors are used to monitor for leakage and ensure that rooms are safe to enter after the bio-decontamination cycle.

The technology can be used to decontaminate entire wards or units where necessary.

Two studies have also concluded that the 'routine' use of Bioquell HPV in hospitals is operationally feasible.

Many of these important features, including repeatability, homogeneous 3D distribution, catalytic aeration removal systems, active health and safety monitoring, remote control, capacity for ward-scale decontamination and government accreditation are lacking for aHP systems.

According to one report, the downtime associated with one aHP system is 4-5 hours per room.

This would make regular use of aHP devices impractical in a busy hospital environment.