Antibiotics can kill ‘good’ bacteria in the human gut leaving pathogenic strains to survive, which poses a risk of causing gut infections.

There are growing concerns about the overuse of antibiotics contributing to the global public health threat of drug-resistant bacterial infections in humans (a topic of concern reported on regularly by the Digital Journal).

In a study published in Nature, researchers have found that a number of intestinal pathogens can cause problems after antibiotic administration. This seems to be because during the first twenty-four hours after administration of oral antibiotics, a spike in carbohydrate availability takes place within the gut.

The carbon causes a peak in available nutrients. When this is combined with the act of most antibiotics to kill of beneficial bacteria in the gut, this creates conditions for pathogenic strains to potentially grow to harmful levels. In a health functioning gut the beneficial bacteria out-compete the harmful bacteria.

Studies have shown that antibiotics can severely affect the gut-microbe ecosystem, and it takes a few days to recover after a dose of antibiotics and it can take a month or more for the gut to regain its former numbers of beneficial bacteria.

To explore this further, the research team experimented on mice that had been born and bred in a germ-free environment. The guts of the mice were devoid of bacteria, unlike normal mice. By experimenting with antibiotics and introducing different strains of bacteria, the scientists showed how antibiotics can create conditions within which pathogenic bacteria can flourish.

This finding adds to evidence the bacteria in the human gut are part of a complex microbial ecosystem, where disruptions can cause health issues like obesity. The published paper is titled “Microbiota-liberated host sugars facilitate post-antibiotic expansion of enteric pathogens.”