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 µg/mL to 15 µg/mL for planktonic cultures, and 3 µg/mL to 20 µg/mL for the biofilm growth of uropathogenic bacteria. Furthermore, the minimum biofilm eradication concentration assay demonstrated that 200-1000 µg/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 µg/mL for E. coli, and 1000 µg/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).

No description available.

Quaternary ammonium compounds (QACs) have long served as lead disinfectants in residential, industrial, and hospital settings. Their simple yet effective amphiphilic nature makes them an ideal class of compounds through which to explore antibacterial activity. We have developed novel multiQAC scaffolds through simple and cost-efficient syntheses, yielding hundreds of diverse compounds strategically designed to examine various aspects of antibacterial and anti-biofilm activity, as well as toxicity. Many of these bis-, tris-, and tetraQACs display antibacterial activity 10 to 100 times greater than conventional monoQACs, and are among the most potent biofilm eradicators to date. Through analyzing their activity against several strains, we have uncovered and provided further evidence for key tenets of amphiphilic QAC bioactivity: a balance of hydrophobic side chains with cationic head groups generates optimal antibacterial activity, though toxicity to eukaryotic cells needs to be mitigated. Given their ubiquitous nature and chemical robustness, the overuse of QACs has led to the development of QAC resistance genes that are spreading throughout the microbial world at an alarming rate. These resistant strains, when found in bacterial biofilms, are able to persist in the presence of lead commercial QAC disinfectants, warranting the development of next-generation biocides. Several of our scaffolds were designed with QAC resistance machinery in mind; thus, we utilized these compounds not only as antibacterial agents but also as chemical probes to better understand and characterize QAC-resistance in methicillin-resistant Staphylococcus aureus (MRSA). Our findings support previous postulations that triscationic QACs would retain potency against QAC-resistant strains. Furthermore, we have identified monocationic and aromatic moieties, as well as conformational rigidity, as being more prone to recognition by the resistance machinery. Using our chemical toolbox comprised of QACs of various charge state and scaffold, we explored both the mechanism and scope of QAC-resistance by examining their structure-resistance relationship. Our holistic findings have allowed us to better understand the dynamics of this system towards the design and development of next-generation QACs that will: (1) allow us to better probe the resistance machinery, and (2) remain efficacious against a variety of microbial pathogens. / Chemistry

Mechanisms of adsorption of alkaline copper quat (ACQ) components in wood were investigated with emphasis on: copper chemisorption, copper physisorption, and quat adsorption. Various factors were investigated that could affect the adsorption of individual ACQ components in red pine wood. Copper chemisorption in wood was affected by ligand types coordinating with Cu and the stability of the Cu-ligand complexes in solution. For Cu-monoethanolamine (Cu-Mea) system, the prevailing active solvent species at the solution pH, [Cu(Mea)2-H]+ complexes with wood acid sites and loses one Mea molecule through a ligand exchange reaction. The amount of adsorbed Cu was closely related to the cation exchange capacity of wood. An increase in Mea/Cu ratio increased the proportion of the uncharged Cu-Mea complex and resulted in decreased Cu chemisorption in wood. Copper precipitation is also an important Cu fixation mechanisms of Cu-amine treated wood. X-ray diffraction analysis revealed that in vitro precipitated Cu was a mixture of copper carbonates (azurite and malachite) and possibly Cu2O. Higher concentration Cu-amine solutions retarded the Cu precipitation to a lower pH because of higher free amine in the preservative-wood system. The changes in zeta potential of wood in relationship to the quaternary ammonium (alkyldimethylbenzylammonium chloride: ADBAC) adsorption isotherm showed two different adsorption mechanisms for quat in wood: ion exchange reaction at low concentration and additional aggregation form of adsorption by hydrophobic interaction at high concentration. Because of the aggregation effect, when wood was treated with ACQ, high amounts of ADBAC were concentrated near the surface creating a steep gradient with depth. This aggregated ADBAC was easily leached out while the ion exchanged ADBAC had high leaching resistance. Free Mea and Cu of ACQ components appeared to compete with ADBAC for the same bonding sites in wood.

Mechanisms of adsorption of alkaline copper quat (ACQ) components in wood were investigated with emphasis on: copper chemisorption, copper physisorption, and quat adsorption. Various factors were investigated that could affect the adsorption of individual ACQ components in red pine wood. Copper chemisorption in wood was affected by ligand types coordinating with Cu and the stability of the Cu-ligand complexes in solution. For Cu-monoethanolamine (Cu-Mea) system, the prevailing active solvent species at the solution pH, [Cu(Mea)2-H]+ complexes with wood acid sites and loses one Mea molecule through a ligand exchange reaction. The amount of adsorbed Cu was closely related to the cation exchange capacity of wood. An increase in Mea/Cu ratio increased the proportion of the uncharged Cu-Mea complex and resulted in decreased Cu chemisorption in wood. Copper precipitation is also an important Cu fixation mechanisms of Cu-amine treated wood. X-ray diffraction analysis revealed that in vitro precipitated Cu was a mixture of copper carbonates (azurite and malachite) and possibly Cu2O. Higher concentration Cu-amine solutions retarded the Cu precipitation to a lower pH because of higher free amine in the preservative-wood system. The changes in zeta potential of wood in relationship to the quaternary ammonium (alkyldimethylbenzylammonium chloride: ADBAC) adsorption isotherm showed two different adsorption mechanisms for quat in wood: ion exchange reaction at low concentration and additional aggregation form of adsorption by hydrophobic interaction at high concentration. Because of the aggregation effect, when wood was treated with ACQ, high amounts of ADBAC were concentrated near the surface creating a steep gradient with depth. This aggregated ADBAC was easily leached out while the ion exchanged ADBAC had high leaching resistance. Free Mea and Cu of ACQ components appeared to compete with ADBAC for the same bonding sites in wood.

No description available.