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. 2022 Feb 17;19(4):2325.
doi: 10.3390/ijerph19042325.

Antimicrobial Photodynamic Coatings Reduce the Microbial Burden on Environmental Surfaces in Public Transportation-A Field Study in Buses

Larissa Kalb  1 , Pauline Bäßler  1 , Wulf Schneider-Brachert  2 , Daniel Bernhard Eckl  3
Affiliations

Antimicrobial Photodynamic Coatings Reduce the Microbial Burden on Environmental Surfaces in Public Transportation-A Field Study in Buses

Larissa Kalb et al. Int J Environ Res Public Health. .

Abstract

Millions of people use public transportation daily worldwide and frequently touch surfaces, thereby producing a reservoir of microorganisms on surfaces increasing the risk of transmission. Constant occupation makes sufficient cleaning difficult to achieve. Thus, an autonomous, permanent, antimicrobial coating (AMC) could keep down the microbial burden on such surfaces. A photodynamic AMC was applied to frequently touched surfaces in buses. The microbial burden (colony forming units, cfu) was determined weekly and compared to equivalent surfaces in buses without AMC (references). The microbial burden ranged from 0-209 cfu/cm2 on references and from 0-54 cfu/cm2 on AMC. The means were 13.4 ± 29.6 cfu/cm2 on references and 4.5 ± 8.4 cfu/cm2 on AMC (p < 0.001). The difference in microbial burden on AMC and references was almost constant throughout the study. Considering a hygiene benchmark of 5 cfu/cm2, the data yield an absolute risk reduction of 22.6% and a relative risk reduction of 50.7%. In conclusion, photodynamic AMC kept down the microbial burden, reducing the risk of transmission of microorganisms. AMC permanently and autonomously contributes to hygienic conditions on surfaces in public transportation. Photodynamic AMC therefore are suitable for reducing the microbial load and closing hygiene gaps in public transportation.

Keywords: AMC; antimicrobial coating; photodynamic inactivation; public transportation.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Figure 1
Figure 1
(A) Sampling sites of the public transport buses. Sites 1–3 were surfaces frequently touched by the operator including two door opening buttons (1, 2) and the steering wheel (3). Sampling sites 4–6 were frequently touched surfaces in the passenger part of the bus, including a stop button (4), a textured handrail (5) and a nontextured handrail (6). (B) The values of microbial burden of the prestudy sampling are shown as box plots with the median and the quartile ranges.
Figure 2
Figure 2
Results from laboratory experiments. The illuminated sample with photosensitizer in the coating achieves a logarithmic reduction exceeding 4 log10 steps (blue bar), while dark control (pink bar) and the recovery control (recovery control) led to no noteworthy bacterial reduction. Error bars represent the standard deviation of the experiments (n = 5).
Figure 3
Figure 3
The values of microbial burden on uncoated references and on antimicrobial coatings are shown as box plots with the median and the quartile ranges.
Figure 4
Figure 4
The mean values for all 14 samplings. The regression line indicates an almost constant difference between uncoated references without antimicrobial effect and the sites with the antimicrobial coating.
See this image and copyright information in PMC

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