Evolving E. coli strains from farm animals to humans

E. coli usually live as harmless bacteria in the gastrointestinal tracts of birds and mammals but also reside in environments such as water and soil and in food products, such as turkey and chicken meat. E. coli is the primary source of urinary tract infections and can also lead to sepsis and meningitis.

An emerging drug-resistant strain of E. Coli

The study led by the University of Technology Sydney, aimed to better understand the evolution and genomic characteristics of an emerging strain of E. coli, known as ST58, which is on the rise, particularly in parts of Europe, and which is also more drug-resistant.

Dr Cameron Redi, from the university, said: “Our team analysed E. coli ST58 genomes from more than 700 human, animal, and environmental sources around the world, to look for clues as to why it is an emerging cause of sepsis and urinary tract infections. We found that E. coli ST58 from pigs, cattle and chickens contain pieces of genetic material, called CoIV plasmids, which are characteristic of this strain of disease-causing E. coli.”

Plasmids are tiny double-stranded DNA molecules, separate from the bacterial chromosome, that can replicate independently and transfer across different E. coli strains, aiding the evolution of virulence. Acquisition of CoIV plasmids may prime E. coli strains to cause additional intestinal infections in humans, and also increase the likelihood of antimicrobial resistance, according to the research.

“Zoonosis, particularly in relation to E. coli, should not be viewed simply as the transfer of a pathogen from an animal to a human,” said research co-author, Professor Steven Djordjevic. “Rather, it should be understood as a complex phenomenon arising from a vast network of interactions between groups of E. coli (and other bacteria), and the selective pressures they encounter in both humans and animals,” he said.

Poultry as part of the evolution of this pathogen

The findings suggest all 3 major sectors of food animal production (poultry, cattle and pigs) have acted as backgrounds for the evolution and emergence of this pathogen.

The study has broad implications for public health policy that spans across the food industry, veterinary and clinical settings, according to Dr Reid.

“Ideally, with the advent and widespread uptake of genome sequencing technology, future infectious disease public health can transition to a primarily pro-active discipline, where genomic surveillance systems are able to predict pathogen emergence and inform effective interventions.”

For such a system to work, ongoing collaboration between governments, public health bodies, food producers, and clinicians is needed, and it would involve surveillance of a variety of non-human sources of microbes.

“This would include domestic and wild animals – particularly birds – food products, sewerage, and waterways – in what is referred to as a ‘One Health’ approach. Some microbes, like ST58 E. coli, know very few barriers between these increasingly interconnected hosts and environments.

“A One Health genomic pathogen surveillance system would be a revolution within public health and do much to break down historically human-centric approaches devoid of connection with the world around us.”

*A role for CoIV plasmids in the evolution of pathogenic Escherichia coli ST58 has been published in the journal Nature Communications