Pre-clinical impact of environmental dry surface biofilms in healthcare settings

Harsent, Ruby 2026. Pre-clinical impact of environmental dry surface biofilms in healthcare settings. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

Dry surface biofilms (DSB) threaten clinical and food settings globally. These allow the transfer of pathogenic organisms to hands or gloves for further dissemination, cannot be detected by swabbing alone, and have low susceptibility to disinfectants. Vancomycin-resistant enterococci is a threat- however it was unknown if this infective agent could form and persist in single species DSB. This thesis explores the formation of artificial Enterococcus spp, DSB on ten different surfaces and investigated how the qualities of ten different surfaces affected DSB culturability. DSB persisted on stainless steel for over a year in high concentrations, highlighting the importance of proper disinfection and removal. The characteristics of artificial Enterococcus spp. DSB was explored, such as the antibiotic-resistant phenotype post-DSB, the composition, and the metabolism. The latter of which addressed a gap in the literature which was only theorised up until this point. This thesis also aimed to address the lack of non-destructive sampling methods for DSB and identified one method with future potential for low-cost use in healthcare and the food industry. Although currently used disinfectants and formulations were ineffective against DSB based on standard disinfectant efficacy testing guidelines for planktonic bacteria dried on to surfaces (not biofilm), some peracetic acid-based formulated disinfectant products were successful in reducing DSB to undetectable levels. Transferability and regrowth were not tested. The most successful formulation employed a combination of mechanical action and the disinfectant to reduce the DSB to undetectable levels. Finally ultraviolet light-based disinfection was not effective against Enterococcus spp. at the settings tested (13 min of 254 nm UV-C treatment). This work concludes that peracetic acid-based formulations are effective at reducing DSB on surfaces, and that an agreed upon method of forming artificial DSB must be solidified.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Schools > Pharmacy
Subjects:	Q Science > Q Science (General)
Date of First Compliant Deposit:	23 June 2026
Last Modified:	23 Jun 2026 14:42
URI:	https://orca.cardiff.ac.uk/id/eprint/187700

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