Antimicrobial Surface Coatings For Controlling Transmission Of Infection

Paulukiewicz, Benedict

Abstract

When patients undergo significant medical treatment, they will often spend multiple days in
hospital. As a result of this prolonged stay in healthcare settings the risk of developing an
infection increases. Infections which arise during a stay in a healthcare setting, or shortly after
leaving a healthcare setting are commonly referred to as health care associated infections.
Health care associated infections are often bacteria surviving on many of the surfaces found
in a hospital. Many of the bacteria found in hospitals belong to a group of pathogens known
as the ESKAPE pathogens. The ESKAPE pathogens are a group consisting of Escherichia coli,
Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii,
Pseudomonas aeruginosa and Enterococcus sp.. These species are all highly monitored and are
often the cause of many healthcare infections.
To combat this, infection control interventions are required to break the chain of infection
from health care setting to patient.
The standard material used for hospital surfaces is stainless steel due to its corrosion resistance. As stainless steel does not naturally possess antimicrobial properties, ESKAPE pathogens
can reside on these untreated surfaces in between periods of cleaning. Copper is effective as an
antimicrobial coating but has not yet been widely adopted because of the additional cost and
the additional factors in the manufacture of copper coated items.
The objective of this study was to investigate the effectiveness of copper and titanium coated
stainless steel surfaces produced using chemical vapour deposition (CVD) method in reducing
healthcare associated infections caused by ESKAPE pathogens.
We hypothesize that the dual-action of CuTiO2 surfaces can provide an effective way of
reducing bacterial transmission in a real world environment.
CuTiO2 surfaces utilize a dual action antimicrobial killing mechanism. The UV generation of
free radicals and oxidative species obtained from the titanium dioxide is combined with copper,
which utilises its ionic charge as a lewis acid, to kill microbes.
A new biofouling method was developed to ensure consistency in colony counts and antimicrobial surface testing. Copper and titanium were deposited onto stainless steel using CVD method
to create photocatalytic surfaces. The effectiveness of CuTiO2 surfaces in reducing bacterial
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survival was tested using viable S. aureus NCTC 8532 and BacLight Live/Dead staining along
with agarose plate transfer counts.
Preliminary investigations into the effects of CuTiO2 surfaces on antimicrobial susceptibility
of isolates exposed to CuTiO2 surfaces were also investigated. Culture and 16S rRNA-based
techniques were used to test CuTiO2 activity in an uncontrolled real world environment, and
were placed in a university toilet open to students and staff.
CuTiO2 surfaces demonstrated a marked decrease in viable S. aureus NCTC 8532 and E. coli
01210 cells within 120 minutes compared to untreated stainless steel (p=0.021 after 1 minute,
and p=0.0055 after 60 minutes). The use of UV irradiation increased bacterial killing. Analysis
using BacLight Live/Dead staining confirmed a reduction in bacterial survival within 60 minutes
compared to un-coated controls (p=0.0054). Preliminary investigations into antibiotic resistance
of isolates exposed to CuTiO2 surfaces showed increased susceptibility to certain antibiotic compounds than un-coated and standard strain controls (p=0.03 and p=0.02 respectively). CuTiO2
surfaces were found to only contain isolates with natural copper resistance genes such as copA
and copZ, and the main species found on these surfaces were Micrococus luteus and Bacillus
altitudinis respectively.
Phylogenetic analysis revealed closely related bacterial species forming various clusters, suggesting that resistant bacteria persisted on CuTiO2 surfaces but were not identical clones. Tetracycline resistance was found in most isolates, across all samples (n=14) and formed two evolutionary branches similar to the presence of merR1, a highly conserved mercury resistance gene.
In conclusion, copper and titanium coated stainless steel surfaces produced using CVD
method have potential as simple, cost-effective, and durable antimicrobial surfaces that can
reduce healthcare associated infections caused by ESKAPE pathogens. CuTiO2 surfaces demonstrated antimicrobial activity against S. aureus NCTC 8532 and E. coli 01210 and increased
susceptibility to certain antibiotic compounds. However, further research is needed to investigate
the long-term effectiveness of CuTiO2 surfaces in reducing healthcare associated infections in a
hospital environment.

Citation

Paulukiewicz, B. (2024). Antimicrobial Surface Coatings For Controlling Transmission Of Infection. (Thesis). University of Salford

• Thesis Type: Thesis
• Deposit Date: Dec 12, 2023
• Publicly Available Date: Apr 27, 2024
• Award Date: Mar 26, 2024