Scientists identify how harmless gut bacteria turn bad

An international team of scientists has determined how harmless E. coli gut bacteria in chickens can easily pick up the genes required to evolve to cause a life-threatening infection. Their study, published in Nature Communications, warns that such infections not only affect the poultry industry but could also potentially cross over to infect humans.

E. coli is a common bacterium that lives in the intestines of most animals, including humans. It is usually harmless when it stays in the gut, however it can become very dangerous if it invades the bloodstream, causing a systemic infection that can even lead to death.

Avian pathogenic E.coli (APEC) is most common infection in chickens reared for meat or eggs. It can lead to death in up to 20 per cent of cases and causes multi-million pound losses in the poultry industry. The problem is made worse by increasing antibiotic resistance and infections also pose a risk of causing disease in humans.

The team of scientists, led by the Milner Centre for Evolution at the University of Bath, sequenced and analyzed the whole genomes of E. coli bacteria found in healthy and infected chickens bred at commercial poultry farms to better understand why and how these normally innocuous bugs can turn deadly.

They found there was no single gene responsible for switching a harmless bacterium into a pathogenic one, but rather that it could be caused by several combinations of a diverse group of genes.