Inhibiting and Characterising Biofilms Formed by Gram-negative Uropathogenic Bacteria

Urinary catheters are indispensable in healthcare and, with an ageing population, their use will continue to increase. However, they are commonly associated with colonisation and urinary tract infections (UTIs) caused by the attachment of bacteria to the catheter surface. Application of a novel cationic compound as a catheter coating may have a significant impact on the costs associated with treatment of UTIs and reduce the need for catheter replacement, as well as decreasing the number of UTI associated morbidity and mortality. Cationic compounds in particular are known to interact with the negatively charged outer membrane of bacteria, therefore have a broad spectrum of activity. The purpose of this study was to source and evaluate a novel cationic antimicrobial for use as a potential coating to impede biofilm formation on urinary catheters, and to investigate the cellular response to the selected lead compound. This research has demonstrated that the antimicrobial activity of commercially available Byotrol? was superior to that of polyamines and quaternary ammonium compounds that were screened. Using high-throughput antimicrobial assays, such as the minimum inhibitory concentration and microtitre plate biofilm forming assays, the inhibitory concentrations of Byotrol? were found to range from 3 �g/mL to 15 �g/mL for planktonic cultures, and 3 �g/mL to 20 �g/mL for the biofilm growth of uropathogenic bacteria. Furthermore, the minimum biofilm eradication concentration assay demonstrated that 200-1000 �g/mL Byotrol? was able to eradicate an established biofilm. Byotrol? may also have significant potential as a device coating, as pre-coating data on glass slides and microtitre plates with the compound inhibited bacterial growth on the surface at concentrations of 400 �g/mL for E. coli, and 1000 �g/mL K. pneumoniae. Atomic force microscopy validated the expectation that higher concentrations of Byotrol? coated a surface more evenly than lower concentrations. Using two-dimensional gel electrophoresis, the metabolic protein tryptophanase was seen to be significantly over-expressed when E. coli K12 was treated with sub-inhibitory concentrations of Byotrol? A transcriptomic approach using RNA-Seq demonstrated that a majority of the differentially expressed genes were identified in cells that were challenged with 4 times the minimum inhibitory concentration of Byotrol? Genes associated with protein synthesis and stress response were significantly up-regulated. Interestingly, the global gene regulators AI-2 and indole were significantly up-regulated, which may have an influence on the expression of genes related to motility, biofilm formation and acid-resistance. Genes associated with chemotaxis and motility, acid-resistance and iron transport were significantly down-regulated, particularly in cells challenged with Byotrol? Byotrol? displayed antimicrobial activity both in suspension and as a coating. Identification of differentially expressed genes and proteins, when the bacteria were treated and challenged with Byotrol? , has, for the first time, revealed the bacterial cell? s response to this biocide. The findings may enable the development of strategies to prevent or better manage catheter associated urinary tract infection (CAUTI).