Antibiotics may boost harmful gut bacteria

Scientists have found that taking antibiotics can change the gut microbiota by increasing nutrients which benefit the growth of pathogens such as salmonella, known to cause many human diseases.
Identifying a mechanism responsible for altering microbial communities opens the door to the development of new therapies designed to interrupt the chain of events that give these pathogens a growth advantage after antibiotic treatments, the researchers said.
"Research has traditionally focused on the mechanisms by which antibiotics help control the growth of bacteria or inform the development of new formulations when bacteria become resistant to existing drugs," said Franziska Faber, from the University of California, Davis (UC Davis).

"But our research study is the first to show that Salmonella was able to flourish in the gut after antibiotic treatment because of the increased availability of oxidised sugars," Faber said.
Gastroenteritis is a common side effect of taking antibiotics.
While diarrhoea may be mild and clear up after antibiotic therapy is completed, in some cases, it can lead to colitis, an inflammation of the colon, or more serious conditions that cause abdominal pain, fever and bloody diarrhoea.

Researchers found that oral antibiotic treatment increased the synthesis of a host enzyme that generates nitric oxide radicals, which can oxidise sugars into sugar acids, such as galactarate, a key driver of Salmonella growth.

"Taxonomists identified galactarate utilisation empirically as a characteristic of Salmonella isolates causing gastroenteritis," Andreas Baumler, professor at UC Davis.
"The new study suggests that this property is part of a 'business plan' Salmonella uses to grow in the host intestine," he said.
The study was published in the journal Nature.