Chloramphenicol, Frogs…and Bacterial Endosymbionts?

If don’t already know, the world’s frog (and other amphibian) populations are facing a massive decline. One cause is an infection by chytridiomycosis, a fungal disease. Scientists in New Zealand have announced that treatment with chloramphenicol, an antibacterial agent can cure chytridiomycosis:

Fearful that chytridiomycosis might wipe out New Zealand’s critically endangered Archey’s frog (Leiopelma archeyi), the researchers have been hunting for a compound that would kill off the disease’s trigger, the fungus Batrachochytrium dendrobatidis.
They tested the chloramphenicol candidate on two species introduced to New Zealand from Australia: the brown tree frog (Litoria ewingii) and the southern bell frog (L. raniformis).
“We found that we could cure them completely of chytrids,” said Phil Bishop from the University of Otago.
“And even when they were really sick in the control group, we managed to bring them back almost from the dead.”
“You could put them on their back and they just wouldn’t right themselves, they would just lie there. You could then treat them with chloramphenicol and they would come right,” Dr Bishop explained.
But the Zoological Society of London (ZSL) expressed caution at the news. Wildlife epidemiologist Dr Trent Garner said there would be reluctance to take up chloramphenicol as a solution, certainly in Europe and North America, because of the chemical’s link to harmful side-effects in humans.

I don’t have a problem using chloramphenicol to treat individual frogs, particular members of endangered species. But I don’t see how this could be used at a population-wide level. We do not want to bathe significant swathes of the globe in a dilute solution of chloramphenicol. Not only can chloramphenicol be toxic to humans*, but chloramphenicol resistance in bacteria is often linked to other antibiotic resistances–that is, chloramphenicol resistant bacteria are often resistant to other drugs.
Nonetheless, it might be useful in certain situations. It’s also interesting that chloramphenicol works against a fungus. I’m wondering if the fungus has a bacterial endosymbiont that plays an important role in causing disease: the chloramphenicol might be killing the endosymbiont, making the fungus unable to cause disease. This isn’t weird: many eukaryotes have bacterial endosymbionts (some obligate, some acquired through infection) that can be ‘cured’ (removed) by antibiotic therapy.
*The medicinal benefits of not dying from a bacterial infection usually outweigh the toxic side effects of antibiotic therapy–which is the case for many antibiotics. It’s also a good reason why you shouldn’t take antibiotics without a doctor’s advice.

This entry was posted in A Fungus Among Us, Antibiotics, Froggies, Microbiology. Bookmark the permalink.

3 Responses to Chloramphenicol, Frogs…and Bacterial Endosymbionts?

  1. Stephanie Boyd says:

    Hi Mike,
    I enoyed the post. I think you might be confounding bacterial with fungal diseases however.

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