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Impact of protective bacteria linked to infection route, finds new study from the University of Edinburgh

The benefits of protective bacteria – which safeguard organisms from further disease without causing harm – depend on how subsequent infections enter the body.

Drososphila melanogaster

Scientists made their discovery studying the bacteria Wolbachia, which in itself does not cause disease but benefits its thousands of host species in many ways, including protecting from other infections.

They found that insects which carried Wolbachia and then contracted another infection through feeding – as they would in the wild – fought disease better than those which had the same infection injected into their bodies.

Researchers say that studies which focus on natural routes of infection could improve our understanding of immunity in many species.

Their study also confirms that Wolbachia – which is known to provide protection from bacterial infections in other insect species – offers the same benefit in flies.

Wolbachia can provide protction from bacterial co-infection

In their studies, researchers from the University of Edinburgh studied bacterial infection in fruit flies, some of which were already carrying Wolbachia bacteria.

When infected with a second bacterial infection – either orally or by injection – flies carrying Wolbachia which had been infected orally were best able to fight the disease. Further analysis showed these flies’ immune systems had triggered production of antimicrobial and detoxifying molecules in response to the infection.

Researchers also found that male flies experienced greater disease protection with Wolbachia than females, and suggest a greater focus on differences in immune response to infection between the sexes.

The study, published in Proceedings of the Royal Society B, was supported by the Wellcome Trust and by Society in Science (ETH Zurich).

Read the paper:  Gupta V, Vasanthakrishnan RB, Siva-Jothy J, Monteith KM, Brown SP, Vale PF. 2017 . Proc. R. Soc. B 284: 20170809. The route of infection determines Wolbachia antibacterial protection

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