RESEARCH ▶▶▶
Evolving E. coli strains from farm animals to humans
Research suggests that genetic material from E. coli bacteria in farm animals, including poultry, could be contributing to the evolution of deadly pandemic strains in humans.
BY TONY MCDOUGAL E . coli usually live as harmless bacteria in the gastroin-
testinal tracts of birds and mammals but also reside in environments such as water and soil, and can be found 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. The study, led by the University of Technology, Sydney, aimed to gain a better understanding of 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 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-inducing E. coli.”
Plasmids are tiny double-stranded DNA molecules, separate from the bacterial chromosome, that can replicate inde- pendently and transfer across different E. coli strains, aiding the evolution of virulence. Acquisition of CoIV plasmids may prime E. coli strains to cause extra intestinal infections in hu- mans and 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-au- thor Professor Steven Djordjevic. “Rather, it should be under- stood 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.
Broad implications The findings suggest all three major sectors of food animal production (poultry, cattle and pigs) have provided suitable background conditions for the evolution and emergence of this pathogen. The study has broad implications for public health policy spanning the food industry, veterinary and clini- cal areas, according to Dr Reid. “Ideally, with the advent and widespread uptake of genome sequencing technology, fu- ture infectious disease public health can transition to a pri- marily pro-active discipline, where genomic surveillance sys- tems 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 clini- cians is needed and would involve the monitoring of a varie- ty of non-human sources of microbes. “This would include domestic and wild animals – particularly birds – food prod- ucts, sewerage and waterways – in what is often referred to as a ‘One Health’ approach. Some microbes, like ST58 E. coli, encounter very few barriers between these increasingly in- terconnected hosts and environments. “A One Health genomic pathogen surveillance system would be a revolu- tion in public health and do much to break down historically human-centric approaches, devoid of connection with the world around us.”
Research suggest that all three major sectors of food animal production (poul- try, cattle and pigs) have provided suitable background conditions for the evolution and emergence of E. coli.
34 ▶ POULTRY WORLD | No. 2, 2022
A role for CoIV plasmids in the evolution of pathogenic Escherichia coli ST58 was published in the journal Nature Communications.
PHOTO: MARK PASVEER
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