20-Feb-2012

Rainforest plant combats multi-resistant bacterial strains

A Danish scientist has discovered a natural substance in a Chilean rainforest plant that becomes active when combined with antibiotics.

Jes Gitz Holler from the University of Copenhagen has found a compound in a research project that targets a particular resistance mechanism in Staphylococcus aureus, the most common cause of infection in wounds from an operation. The development of resistance in these bacteria is rapid. Bacterial strains that do not respond to treatment have already been found in the US and Greece.

‘Resistant bacteria have an efflux pump in their bacterial membrane that efficiently pumps out antibiotics as soon as they have gained access,’ explained Holler. ‘The identified natural substance inhibits the pumping action, so that the bacteria’s defence mechanisms are broken down and the antibiotic treatment allowed to work.’

Holler gathered specimens of the plant, which comes from the Persea family, in Chile, where the Mapuche people use the leaves of the avocado plant to heal wounds. The results have been published in the Journal of Antimicrobial Chemotherapy.

The MIC value is the lowest possible concentration of an antibiotic that inhibits bacterial growth. With his compound, Holler says he can lower the MIC value by at least eight times.

‘The natural compound has great potential and perhaps in the longer term can be developed into an effective drug to combat resistant staphylococci.

‘At this time there are no products on the market that target this same efflux-inhibitor mechanism. We want to improve the active substance using synthetic chemistry in the laboratory. That will also ensure sustainable production of a potential drug while protecting rainforest plants,’ he added.

Holler said a commercial product would benefit the Mapuche people. At present there is a written agreement between the Faculty of Health and Medical Sciences at the University of Copenhagen and the representative of the Mapuche people, Alfonso Guzmán, who helped procure the plant material.

As well as causing infection in wounds after surgery, Staphylococcus aureus can be the cause of many diseases, from abscesses and food poisoning to life-threatening infections such as infective endocarditis and sepsis. The bacteria have been a major problem in hospitals worldwide since the 1940s, and up to now the drug industry has managed to develop new antibiotics in step with the increasingly aggressive behaviour of the bacteria. Unfortunately, that development appears to be turning.

Holler suggests that as treatment options become more scarce owing to the high costs involved in developing new antibiotics, research will have to find new paths and natural substances could be one of them.

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