Strategies that aim to combat microbes with "more friendly" strains are highly risky, British researchers have warned.
A study at Exeter University has found that this kind of treatment could backfire badly with "devastating consequences."
The researchers say that up to now studies have suggested the strategy could be effective – and have shown encouraging results in tackling C.difficile.
The strategy involves introducing weak strains into a population of disease-causing microbes – in the hope that they will replace bacteria that cause disease.
The scientists conducted a laboratory study into the fungus that causes rice blast disease. They found that the introduction of "pacifist" mutant strains proved counter-productive, leading to disease of increased severity.
They have backed their work with mathematical studies showing how the strategy can go wrong as pathogens behave in unpredictable ways.
The findings have been reported in the journal eLife.
Researcher Professor Ivana Gudelj said: "Our study shows that a promising disease management strategy may not always be effective and indeed may have damaging unforeseen consequences. Importantly, our work also provides a foundation for the analysis of when, and why, this can happen.
"We find that the mechanisms driving our unexpected findings when treating rice blast infection are pertinent for many diseases involving bacterial and fungal pathogens."
Molecular geneticist Professor Nick Talbot said: "The strategy of introducing less aggressive microbes to fight more aggressive ones may prove effective to control some crop disease, but our study shows that they are not a silver bullet and caution needs to be exercised. We need to understand how microbes interact with each other in natural settings, before we can try to alter their ability to cause disease in this way.
"Our study also shows why mathematicians and biologists need to work together more often, because we would not have understood this phenomenon at all without the mathematical analysis carried out."
eLife 28 December 2016; doi: 10.7554/eLife.18678 [abstract]
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