March 2010 - Issue #9
‘Clingy’ bacteria surprise comes to the surface
Story by Diny Slamet
View articles in related topics: Sustainability & The Environment, Health & Medical
Improving the success rate of artificial implants. Reducing the risk of dangerous Staphylococcus outbreaks in hospitals. Dramatically reducing the amount of fuel oil burned by the world’s merchant shipping fleet. It is a disparate list, but nonetheless it is the set of research goals that a Swinburne University of Technology research team has begun to pursue.
The issues all stem from bacterial activity, in particular the way bacteria adhere to surfaces by creating a ‘biofilm’ that protects the bacteria from the usual sterilisation treatments.
The Swinburne team, working with specialists from Monash University, combines the skills of scientists of different specialisations – microbiology, nanotechnology, engineering and industrial sciences – to seek remedies that cannot be achieved by one discipline alone.
The team is led by microbiologist Professor Elena Ivanova and includes surface chemist Professor Russell Crawford – who is also Dean of Swinburne’s Faculty of Life and Social Sciences – and physical metallurgists Professor Yuri Estrin and Dr Rimma Lapavok from Monash University.
The problems caused by bacteria cost industries such as healthcare, hospitality and shipping billions of dollars each year. The rewards to individuals and society for solving the more intractable problems, such as hospital-borne infections, are immense.
One of the most troublesome issues of modern medicine is infection-related implant failures. According to Professor Ivanova, up to 67 per cent of implants are troubled by bacterial problems. Despite thorough sterilisation processes, this high percentage of medical implants (commonly hips and knees) fail because some types of bacteria attach to the implant as a biofilm, from which they cause further infection. The only solution is to remove the infected implant and replace it.
The research team has already made great strides by disproving a common hypothesis that had previously led researchers down a blind alley. While not a great deal is known about the forces that attract bacteria to solid surfaces, the common hypothesis was that bacteria attach more easily to rougher surfaces because the microscopic valleys on that surface provide shelter from commonly used disinfection processes. Some implant manufacturers are even going down the road of making their products ‘nano-smooth’ so the bacteria cannot find protection from sterilisation processes.
But the scientists have made a surprising discovery. Working with nano-smooth titanium and a range of microbiological analysis techniques, the researchers have found that rather than making it harder for bacteria to adhere to, smooth surfaces seem to be more attractive to some problematic bacteria, with a higher degree of bacterial colonisation on smooth surfaces than on rough.
“The way bacteria attach to nano-smooth surfaces is different to the way they adhere to rough surfaces,” explains Professor Crawford. “The bacteria adhere to these surfaces by secreting an extracellular polymeric substance (EPS), which is a combination of sugars and proteins. This is the first time it has been shown that the EPS is produced in much greater quantities when bacteria come into contact with nano-smooth surfaces, causing a greater amount of bacterial attachment.”
The research suggests that hospitals may have to rethink their disinfection techniques and that manufacturers may have to develop new disinfectants.
“Many bacterial disinfectants used today are based on positively charged (or cationic) surfactants. These attach to the negatively charged bacteria, causing their cell wall to rupture and killing the bacteria. This new research has highlighted the need for disinfectant manufacturers to formulate new products that attack both the EPS and the bacterial cells, and not just the bacterial cells alone,” Professor Crawford says.
Shipping is another industry where the Swinburne research may contribute to a big increase in efficiency. Scientists estimate that a biofilm (or bacterial build-up) the thickness of just a human hair on a ship’s hull can add US$400 an hour to fuel costs because it affects the ship’s drag, causing greater fuel consumption.
Most of the techniques used to limit the build-up of biofilm on ships’ hulls work for a limited time and have a severe ecological downside, with toxic chemicals being used in most marine paints.
The Swinburne research is adding to the body of knowledge that will lead to the development of surface coatings that can reduce the ability of bacteria to build a film on ships’ hulls. This could save the global shipping industry millions of tonnes of oil a year because the ships will be able to move through the water more easily.
The work of the Swinburne scientists is still at the early research stage. “We are really looking at what causes biofilms to form and how well they form on a range of different surfaces. Once we publish our results we hope they will be used by companies to produce more effective disinfection processes and surface coatings,” Professor Crawford says.
