Generally, decontamination of hospital rooms has been
done manually, using traditional applied disinfectant technologies as we have
discussed in previous Disinfectant Chemistry Report Cards. Concerns associated with conventional
cleaning and disinfection methods include: lack of proper cleaning and
disinfection protocols, incompatibility between the disinfectant chemistry and
cleaning substrate (e.g. the cloth...),
operator error (e.g. was the product diluted correctly?), concerns with
unrealistic contact time and if surfaces were actually contacted. In looking for an adjunct to improve the
level of cleanliness in a patient room, a new technology has been developed
which uses ultraviolet light in an automated system to disinfect rooms.
Ultraviolet room disinfection systems use either a
continuous or a pulsed UV lamp. A continuous lamp, which requires a warm-up
period, is powered by low-pressure mercury vapour, and emits light at 253.7 nm,
while a pulsed system (no warm-up required) uses either xenon or krypton gas
with a pulsed emission that ranges from 200 nm to the visible light range. These systems use the same general method;
inactivation of microbes by DNA and/or protein damage. UV light induces
formation of either thymine dimers or thymine-cytosine photoproducts,
preventing microbes from replicating; it is very effective for viruses and
bacteria, and less effective at inactivating fungi and spores.
Compared to H2O2 room disinfection systems, UV systems do
not require room sealing or HVAC shut-off and do not have consumable products
required, though both are residue free and there are no post-cleaning health
concerns. Decontamination times can be significantly reduced with the use of
UV-reflective wall coating. There are some disadvantages that come with a UV
disinfection system. Coverage is a primary concern, as indirect coverage does
not have the same disinfection efficacy that direct exposure does. Equipment
and furniture must be moved away from walls to ensure complete room coverage.
These systems may perform poorly against organisms with inherent resistance, or
ones that can repair themselves; there is evidence that bacteria can evolve UV
resistance when exposed to repeated cycles of low doses. Like other room
disinfection systems, the rooms must be empty and there is a significant
capital investment required. Lastly, UV systems share the same problem that
other disinfection systems have; reduced efficacy with soiled surfaces.
In terms of safety, direct exposure to UV-C radiation is
not fatal, but it can lead to skin and eye irritation.
Continuous lamps contain a very small amount of mercury,
about the same amount as a 4-foot fluorescent bulb, while pulsed UV lamps
contain non-toxic xenon or krypton gas. These systems may be destructive to
metals and plastics/vinyl and cause fading in coloured paints and fabrics. UV
light is known to degrade acetal, acrylonitrile butadiene styrene (ABS),
polyamide (PA) and polycarbonate (PC)-type plastics. A side effect of low dose rates from indirect
exposure is bacterial resistance. Bacteria found at high altitudes have exhibited
resistance to UV light, and bacteria exposed to low doses of UV light can gain
resistance.
Ultraviolet disinfection systems are best for terminal
use and in the ICU or other high-risk infection areas, due to the high capital
cost and the evacuation requirement. They do not eliminate the need for other
infection control and cleaning practices, and are not feasible for hallways,
etc.
Here’s how we would score Ultra Violet Room
Decontamination on the key decision making criteria for room disinfection:
• Speed of Disinfection – B-C
o Cycle time can range from 15 minutes to 45 minutes
depending on room size and system used
o Room preparation is required - furniture must be pulled
away from walls
• Spectrum of Kill – A
o Proven efficacy against all organisms: bacteria,
viruses, fungi, mycobacteria and bacterial endospores
o Requires direct exposure to ensure disinfection will
occur
• Cleaning Effectiveness – D
o Ultraviolet Room Decontamination systems do not
eliminate the need for the physical removal of soils to ensure effectiveness
and provide an aesthetically pleasing
environment
• Safety Profile – B
o Used correctly, the safety concerns can be minimized
• Environmental Profile – A
o No chemicals are used
• Cost Effectiveness – C
o Costs of capital expenditure, labour, and consumables
need to be considered
**For more in-depth scientific information about
Ultraviolet Room Decontamination Devices, stay tuned to
www.infectionpreventionresource.com.
Bugging Off!
Nicole
