Every year about two million people are treated for infections associated with surgical implants and biomedical devices such as catheters, orthopaedic implants and contact lenses at a cost of more than $11 billion in the United States alone.
Adverse consequences resulting from bacterial infections include revision surgery, impaired quality of life of patients, serious health complications and even death, particularly among elderly patients.
A team of University of South Australia researchers has identified a new route towards infection-resistant coatings on biomedical devices by using novel antibacterial chemicals extracted from native plants. Experiments have shown that coatings of these chemicals prevented bacterial colonisation and growth on materials.
Currently bacterial infections that colonise and grow on the surfaces of implants and biomedical devices are protected by a biofilm layer that develops and forms a protective barrier over the bacteria, making it difficult to eradicate by administering antibiotics, according to Ian Wark Research Institute Deputy Director, Professor Hans Griesser, who is leading the research.
“Our research involved attaching antibacterial compounds in thin layers to the surfaces of plastic sheet model materials used for fabricating biomedical devices, and then exposing the samples to bacteria. The results were exciting. The materials coated with the native plant compounds did not allow bacteria to settle, but bacteria happily colonised the uncoated plastic surfaces,” Prof Griesser said.
Prof Griesser has been conducting research with Sansom Institute Research Fellow, Dr Susan Semple, who led the project to extract and identify antibacterial compounds from Australian plants of the genus Eremophila using plant material collected from gardens or the wild, with permits. Eremophila refers to “desert loving”, and these plants prefer dry and arid areas. Some Eremophila species growing in arid areas of Australia are used in traditional Aboriginal medicine.
“As little was known about the active chemicals in these plants, we looked at a whole range of different species of Eremophila, before focusing on plants with a protective resin coating on their leaves, which we believed could be antibacterial,” Dr Semple said.
PhD student, Chi Ndi from the Sansom Institute, School of Pharmacy and Medical Sciences, screened more than 70 different Eremophila species and hybrids and found some that were particularly active against bacteria that cause human medical implant and device infections. Some of the chemicals extracted by Chi Ndi were then coated onto plastics materials by PhD student Hardi Ys from the Ian Wark Research Institute and in collaborative research their antibacterial effectiveness has been studied.
“To our knowledge nobody else in Australia is looking at the biomedical applications of native plants. Having an antibacterial that is completely different to current products being used does have an advantage in that it’s not going to select for resistance to other antibiotics that we need to treat infections,” Dr Semple said.
Being able to isolate compounds with antibacterial effects helps to overcome the limitations of current technologies aimed at fighting infection. It has the potential to deliver a breakthrough solution, with enormous benefits for both human health care and Australian biomedical device manufacturers.
“Some of our research was guided by Aboriginal medicine and an important part of my work has been working with Indigenous people,” Dr Semple said. “But we are not trying to take their medicines and patent them. Our research focuses on the biomedical application in terms of surface coatings, which is quite different to traditional usages,” she said.
“We would like to involve Indigenous communities in establishing and managing the cultivation of the Eremophila species on farms in remote communities and inland,” Dr Semple said.
“In some other antibacterials that we’ve worked with in the past, we’ve encountered a very tight line between being effective against bacteria and damaging human cells. The fact that some Eremophila species have been used by Indigenous people suggested that there was a greater chance that these could be safe,” Prof Griesser said.
“We are patenting a possible solution to implant infections based on encouraging preliminary results and have estimated a two-year timeline to obtain definitive results on the effectiveness of these compounds when applied to several different types of biomedical devices,” he said.
“It’s an exciting glimpse of future possibilities, with a good package of intellectual property including a patent and scientific data to support our findings.”
(Source: Geraldine Hinter: University of South Australia: March 2008)