Antimicrobial efficacy of novel titanium dioxide coating and its potential to Induce changes in adaptive resistance
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
Nosocomial infection is estimated to affect 5% of patients in the United State of America and is likely to be among the top ten causes of early mortality. The first solution that comes to mind is simply hygiene, but the importance of this is often glossed over in favour antibiotics. With rising rates of antibiotic resistance and slowing discovery of new antibiotics, this wellspring is rapidly running dry. Prevention should always be the first option. Improving methods of preventing nosocomial infections is a constant priority. One such method is the use of antimicrobial surface coatings. Metals with antimicrobial agents can be used as self-sterilising coatings.
This thesis focuses on a new formulation of TiO2 called NsARC. This material has been shown to have photocatalytic properties. Photocatalysis is the use of energy from light (most often UV light) directly to carry out a chemical reaction. This action results in antimicrobial effects because it produces reactive oxygen species (ROS) that destabilise the cell membrane and cell wall. Most often photocatalytic materials are limited to activity in ultraviolet (UV) light, but NsARC shows activity in the visible light spectrum
This thesis first focused first on testing the antibacterial activity of NsARC in UV light, ambient visible light and high intensity visible light. It was found that NsARC has bacterial properties and a proportion of that effect can be attributed to photocatalysis. However, a significant portion of the antibacterial activity was shown to be not light dependant and appears to be caused by a different mechanism.
Previous research has found that some antimicrobial materials can induce higher levels of antibiotic resistance, some herbicides for example. The widespread use of such materials can have a detrimental effect on antibiotic resistance. Given that NsARC is a novel antibacterial material being proposed for widespread testing of its effects on antibiotic resistance was thought prudent.
This thesis then focused on the design and construction of three reporter strains as indicators of changes in gene expression associated with changes in antibiotic resistance. Suitability of the reporter strains for investigation of NsARC was tested via exposure to herbicides known to induce antibiotic resistance changes. Two of the strains were shown to be suitable for future testing. A preliminary experiment of the effects of NsARC on one of these reporter strains indicated NsARC may induce higher levels of gene expression associated with increased antibiotic resistance. Testing will continue through the use of the reporter strains.