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Assessment of Ionic Liquids for disinfection of healthcare surfaces

Fallon, Melissa 2019. Assessment of Ionic Liquids for disinfection of healthcare surfaces. PhD Thesis, Cardiff University.
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Surface disinfection for the prevention of healthcare associated infections (HCAI) is well recognised. Ionic liquids (ILs) possess antimicrobial activities that could make their inclusion into disinfectant products beneficial for the control of HCAI. ILs were tested against microorganisms under conditions that affect antimicrobial activity concentration, contact time, organic soiling, and were compared to the commonly used cationic biocides benzalkonium chloride (BZC) and chlorhexidine gluconate (CHX). ILs had potent antimicrobial activity in the presence of organic soiling at a short contact time. At equivalent concentrations, BZC and CHX were not as effective at reducing viability of bacteria and the type of organism and organic soiling hindered the activity. The main factor that affected the antimicrobial activity of formulations was dilution. ILs were unable to inactivate Bacillus subtilis spores but were sporicidal when combined with hydrogen peroxide. Cellular targets of ILs were investigated by potassium leakage from the cell and the uptake of DNA binding dyes. Significant release of potassium from the cell and uptake of dyes into the cell suggested membrane damage was caused by ILs. The ultrastructure of bacteria was assessed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Visually, cells lost structural integrity in a dose-dependent manner. Analysis by AFM shown development of valleys in the structure of Staphylococcus epidermidis. B. subtilis spore mutants lacking protective DNA proteins and spore coat were tested against ILs to assess any interaction of the formulations with intracellular biomolecules. There was no reduction in spore numbers indicating that intracellular components are not targets. Finally, IL formulations were combined with wipe material to assess if antimicrobial activity would translate into a product. As a wet wipe the formulations reduced bacteria without transferring to subsequent surfaces and were more efficacious than commercial wipes. A spill wipe was also developed and was more effective than commercial spill wipes. Formulations were cytotoxic against skin cells in vitro. Overall, ILs displayed greater antimicrobial activity against vegetative bacteria, than BZC and CHX. The proposed mechanism of action is through membrane damage of the cell and as wipe products the ILs were more efficacious than commercial products.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Pharmacy
Subjects: Q Science > Q Science (General)
Date of First Compliant Deposit: 10 March 2020
Last Modified: 10 Mar 2020 17:18

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