Controlling the structure of supramolecular fibre formation for benzothiazole based hydrogels with antimicrobial activity against methicillin resistant Staphylococcus aureus.

Antimicrobial resistance is one of the greatest threats to human health. Gram-positive methicillin resistant Staphylococcus aureus (MRSA), in both its planktonic and biofilm form, is of particular concern. Herein we identify the hydrogelation properties for a series of intrinsically fluorescent, structurally related supramolecular self-associating amphiphiles and determine their efficacy against both planktonic and biofilm forms of MRSA. To further explore the potential translation of this hydrogel technology for real-world applications, the toxicity of the amphiphiles was determined against the eukaryotic multicellular model organism, Caenorhabditis elegans. Due to the intrinsic fluorescent nature of these supramolecular amphiphiles, material characterisation of their molecular self-associating properties included; comparative optical density plate reader assays, rheometry and widefield fluorescence microscopy. This enabled determination of amphiphile structure and hydrogel sol dependence on resultant fibre formation.

Reaction-based indicator displacement assay (RIA) for the development of a triggered release system capable of biofilm inhibition.

Here, a reaction-based indicator displacement hydrogel assay (RIA) was developed for the detection of hydrogen peroxide (H2O2) via the oxidative release of the optical reporter Alizarin Red S (ARS). In the presence of H2O2, the RIA system displayed potent biofilm inhibition for Methicillin-resistant Staphylococcus aureus (MRSA), as shown through an in vitro assay quantifying antimicrobial efficacy. This work demonstrated the potential of H2O2-responsive hydrogels containing a covalently bound diol-based drug for controlled drug release.

Fluoxetine and thioridazine inhibit efflux and attenuate crystalline biofilm formation by Proteus mirabilis.

Proteus mirabilis forms extensive crystalline biofilms on indwelling urethral catheters that block urine flow and lead to serious clinical complications. The Bcr/CflA efflux system has previously been identified as important for development of P. mirabilis crystalline biofilms, highlighting the potential for efflux pump inhibitors (EPIs) to control catheter blockage. Here we evaluate the potential for drugs already used in human medicine (fluoxetine and thioridazine) to act as EPIs in P. mirabilis, and control crystalline biofilm formation. Both fluoxetine and thioridazine inhibited efflux in P. mirabilis, and molecular modelling predicted both drugs interact strongly with the biofilm-associated Bcr/CflA efflux system. Both EPIs were also found to significantly reduce the rate of P. mirabilis crystalline biofilm formation on catheters, and increase the time taken for catheters to block. Swimming and swarming motilies in P. mirabilis were also significantly reduced by both EPIs. The impact of these drugs on catheter biofilm formation by other uropathogens (Escherichia coli, Pseudomonas aeruginosa) was also explored, and thioridazine was shown to also inhibit biofilm formation in these species. Therefore, repurposing of existing drugs with EPI activity could be a promising approach to control catheter blockage, or biofilm formation on other medical devices.