New Scientist - 26.10.2019

14 | New Scientist | 26 October 2019

AN AFRICAN toad has a nifty way

to scare off predators: mimicking

a venomous snake. This strategy

is common in some animal groups,

but is very rare in frogs and toads.

In a 2017 lecture, Eli Greenbaum

at the University of Texas at

El Paso showed a photograph of a

Congolese giant toad (Sclerophrys

channingi). A student named

Theresa Edmondston told him she

kept venomous snakes as pets, and

that the photo looked like the head

of one of her favourites: a Gaboon

viper (Bitis gabonica). The two, as

viewed from above, are compared

in the inset (toad left, snake right).

The pair then explored the idea

with Chifundera Kusamba at the

Natural Sciences Research Centre

in Lwiro, Democratic Republic of the

Congo. He told them that the toads

hiss when approached, which might

make it even easier to confuse them

with snakes (Journal of Natural

History, doi.org/dcx3). ❚

Evolution

A MAN in the US started

producing beer in his gut after

it accidentally became colonised

by high levels of brewer’s yeast.

The normally healthy 46-year-

old began to experience mental

fogginess, dizziness and memory

loss in 2011 and had to give up his

job. He saw multiple doctors, but

they couldn’t work out what was

wrong. A psychiatrist prescribed

him antidepressants in 2014, but

this didn’t help.

A few months later, the man

was arrested for erratic driving.

His blood alcohol reading was

200 milligrams per 100 millilitres,

about the level that would be

expected if he had consumed

20 standard alcoholic drinks.

He said that he hadn’t had

anything alcoholic to drink,

but the police didn’t believe him.

Baffled, the man saw a

gastroenterologist, who

discovered high levels of a

fungus called Saccharomyces

cerevisiae in his stool. This fungus

is also known as brewer’s yeast,

because it is used to convert

carbohydrates into alcohol.

Subsequent tests showed

that a similar conversion process

was happening in the man’s gut.

Every time he ate carbohydrates,

his blood alcohol level shot

up, sometimes to as high as

400 milligrams per 100 millilitres.

In 2017, the man attended a

specialist clinic at Richmond

University Medical Center in

New York, where he was diagnosed

with auto-brewery syndrome.

This case of auto-brewery

syndrome was probably

triggered by a prolonged course

of antibiotics that the man took

in early 2011 for a thumb injury,

says Fahad Malik, one of the

doctors at the centre who

made the diagnosis.

These antibiotics probably

disrupted the man’s balance of

gut microbes, causing abnormal

growth of S. cerevisiae, which

normally exists at low levels in

the human gut, says Malik. He

will present the case at the annual

meeting of the American College

of Gastroenterology this week.

Malik and his colleagues

are the first to describe auto-

brewery syndrome resulting

from antibiotic use. However, it

has also been reported in people

with gut disorders like Crohn’s

disease, most commonly due to

the overabundance of other fungi.

Malik treated the man with

antifungal medication, probiotics

and a low-carb diet to get rid of the

excess brewer’s yeast in his gut.

He has now been symptom-free

for almost two years.  ❚

Microbiome

Man got drunk on beer brewed in his gut

Michael Marshall

Toad that looks like a viper

The amphibian mimics a venomous snake to deter predators

KONRAD MEBERT

News

Alice Klein

“The syndrome was

probably triggered

by a prolonged course

of antibiotics”