An Overview of the Options for Antimicrobial Hard Surfaces in Hospitals - Use of Biocidal Surfaces for Reduction of Healthcare Acquired Infections - page 157

The type of illumination required for photocatalytic activity depends on the
surface. Historically, UV light has been required for photocatalytic activity, but
recent developments mean that photocatalytic activity can be achieved with white
light [ 75 , 110 ]. However, photocatalytic surfaces may not provide 'round the clock'
reduction in contamination because they would be less effective at night where
light levels are lower, depending on the required frequency and duration of
photoactivation.
A number of in situ studies have evaluated the impact of various photosensitisers
in a London Dental clinic [ 74 , 75 ]. Both cellulose acetate impregnated with the
photosensitisers toluidine blue O and rose bengal, and silicon polymers impreg-
nated with gold nanoparticles resulted in significant reductions in TAC. However,
illumination with a lamp close by was used in the study, so efficacy under ambient
light conditions was not assessed.
One study has evaluated the in situ activity of titanium dioxide, which was
applied to surfaces and furniture in a Singaporean critical care unit [ 109 ]. Overall,
untreated samples were significantly more likely to be contaminated with MRSA
or a Gram-negative rods, but treatment with titanium dioxide was not associated
with reduced contamination in multiple logistic regression analysis, suggesting that
other factors are more important for influencing contamination rates. Further
studies of titanium dioxide treated surfaces are required.
7.4.2.4 Polycationic Polymers
Polymers can be combined with antimicrobial agents to produce AMS [ 69 ]. The only
polycationic polymer that has been studied in the healthcare setting is a combination
between polyhexamethylene biguanide (PHMB) with an active polymer (A-200).
The mechanism of action involves a combination of the active polymer, which
immobilises the microbes and PHMB, which disturbs the cell membrane lipid
bilayer. The product achieved a 3-log reduction on S. aureus when applied in
water, but only a 1-log reduction when swabs from clinical specimens (wound and
urine) were applied to surfaces; this difference is probably explained by organic
soiling. The study also included an in situ evaluation of the product, demonstrating a
significant reduction in the TAC on bedside tables. However, the tables were
specifically not cleaned during the study, which was only performed for 24 h after
each application, so further studies are required to assess durability.
7.4.2.5 Triclosan
Triclosan has been widely adopted in a range of consumer markets, but no relevant
in situ studies have been performed in healthcare settings [ 111 , 112 ]. Due to the
high risk of resistance developing, triclosan alone is not an attractive candidate
chemical for AMS.