Browsing by Author "Ronan, Evan"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Species interaction and selective carbon addition during antibiotic exposure enhances bacterial survival
    (Frontiers Media, 2019-11-29) Jackson, Lindsay M. D.; Kroukamp, Otini; Yeung, William C.; Ronan, Evan; Liss, Steven N.; Wolfaardt, Gideon M.
    Biofilms are multifaceted and robust microbiological systems that enable microorganisms to withstand a multitude of environmental stresses and expand their habitat range. We have shown previously that nutritional status alters antibiotic susceptibility in a mixed-species biofilm. To further elucidate the effects of nutrient addition on inter-species dynamics and whole-biofilm susceptibility to high-dose streptomycin exposures, a CO2 Evolution Measurement System was used to monitor the metabolic activity of early steady state pure-culture and mixed-species biofilms containing Pseudomonas aeruginosa and Stenotrophomonas maltophilia, with and without added carbon. Carbon supplementation was needed for biofilm recovery from high-dose streptomycin exposures when P. aeruginosa was either the dominant community member in a mixed-species biofilm (containing predominantly P. aeruginosa and S. maltophilia) or as a pure culture. By contrast, S. maltophilia biofilms could recover from high-dose streptomycin exposures without the need for carbon addition during antibiotic exposure. Metagenomic analysis revealed that even when inocula were dominated by Pseudomonas, the relative abundance of Stenotrophomonas increased upon biofilm development to ultimately become the dominant species post-streptomycin exposure. The combined metabolic and metagenomic results demonstrated the relevance of inter-species influence on survival and that nutritional status has a strong influence on the survival of P. aeruginosa dominated biofilms.
  • Thumbnail Image
    Item
    Surface-attached sulfonamide containing quaternary ammonium antimicrobials for textiles and plastics
    (Royal Society of Chemistry, 2019) Caschera, Alexander; Mistry, Kamlesh B.; Bedard, Joseph; Ronan, Evan; Syed, Moiz A.; Khan, Aman U.; Lough, Alan J.; Wolfaardt, Gideon; Foucher, Daniel A.
    With the risks associated with healthcare-associated infections and the rise of antibiotic resistant microorganisms, there is an important need to control the proliferation of these factors in hospitals, retirement homes and other institutions. This work explores the development and application of a novel class of sulfonamide-based quaternary ammonium antimicrobial coatings, anchored to commercially and clinically relevant material surfaces. Synthesized in high yields (60–97%), benzophenone-anchored antimicrobials were spray-coated and UV grafted onto plastic surfaces, while silane-anchored variants were adhered to select textiles via dip-coating. Surface modified samples were characterised by advancing contact angle, anionic dye staining, X-ray photoelectron spectroscopy and atomic force microscopy. After verifying coating quality through the above characterization methods, microbiological testing was performed on batch samples in conditions that simulate the natural inoculation of surfaces and objects (solid/air) and water containers (solid/liquid). Using the previously established Large Drop Inoculum (LDI) protocol at solid/air interfaces, all treated samples showed a full reduction (105–107 CFU) of viable Arthrobacter sp., S. aureus, and E. coli after 3 h of contact time. Additional testing of the walls of plastic LDPE vials treated with a UV-cured sulfonamide antimicrobial at a solid/liquid interface using the newly developed Large Reservoir Inoculum (LRI) protocol under static conditions revealed a complete kill (>106 reduction) of Gram-positive Arthrobacter sp., and a partial kill (>104 reduction) of Gram-negative E. coli within 24–48 h of contact.