Banishing bad bacteria

30 September 2010

Polymers that can capture harmful bacteria as they pass through the gut have been developed by UK scientists. This could reduce incidence of salmonella poisoning and improve shelf-life of meat products, they claim.

Salmonella, a major food-borne pathogen is a serious problem in the food industry, as well as of clinical and veterinary importance. The 'use-by date' marked on foods reflects the date by which such bacteria will have multiplied to their maximum safe level for consumption.

'If the pathogen level can be lowered at the point of food production, then the shelf-life may become longer and the food safer,' says Mark Bradley at Edinburgh University. In collaboration with Maurice Gallagher, also at Edinburgh University, Bradley's team have identified polymers that bind strongly to a particular strain of salmonella.

Bacteria binding to polymer, as seen on the right, can be removed from the body

Bradley used a polymer microarray - a glass slide with different polymers spotted over its surface - to test the binding ability of hundreds of synthetic polymers in a single experiment. They selected polymers based on the tendency of their monomer building blocks to bind cells and solvate in water, as well as factoring in their availability and affordability.

Scanning electron microscopy and fluorescence imaging allowed the team to determine which polymers bound the bacteria most effectively. In a concurrent study, they also tested the ability of the same polymers to bind to a strain of 'good' bacteria present in the guts of humans and animals.

By comparing the results from both studies, polymers that bind the 'bad' salmonella bacteria while having minimal effect on the beneficial 'good' bacteria were identified. These polymers could be added to commercial feedstuff for animals, such as chickens.

Polymers identified with low binding capacities for salmonella are also useful, says Bradley, as they could be developed into pathogen-repellent coatings on food packaging or medical implants.

'I think what is unique to this approach is the huge throughput,' says Matthias Lutolf at the Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland, an expert in polymeric biomaterials and bioengineering. He adds that 'commercialisation seems possible as the polymers are relatively cheap and the synthesis seems scalable.'

Indeed, Bradley now hopes to develop the polymers for commercial applications and use their initial hits to make subtle improvements to the synthetic polymers to enhance bacteria binding further.

Erica Wise

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