E. coli bacteria can be harmless or harmful to humans depending on its specific genetic makeup. One strain of E. coli, known as ST58, is a growing cause of blood and urinary tract infections in humans, and has also been found to be more drug resistant than other strains of the bacteria. Researchers at the University of Technology Sydney have now tracked the evolution and genomic characteristics of ST58 by analyzing more than 700 ST58 genomes, revealing a link between disease-causing varieties that may have origins in the animals we use for food.
The research team built a collection of more than 752 whole-genome sequences of E. coli ST58 isolates from a range of different sources. These sources included livestock like chickens, pigs and cattle, wild animals, humans with extra-intestinal E. coli infections, plants, surface water and wastewater. The isolates used in the study were collected in a time span ranging from 1970 to 2019, with 92% of the isolates being collected after 2000. The majority of the isolates came from the continents of North America (60%) and Europe (25%).
The team built a core gene phylogeny using the sequences and identified a sublineage featuring a high proportion of sequences containing ColV plasmids. These plasmids are known to have pathogenic properties and contribute to antibiotic resistance, and have also been associated with extraintestinal E. coli infection in humans. The researchers found that most of the ColV-positive sequences were found in samples from humans with such infections, as well as in poultry, porcine, and, to a lesser extent, bovine sources of ST58 E. coli. The ColV-carrying genomes also contained more antimicrobial resistance genes and virulence-associated genes than those without ColV plasmids. This suggests that disease-causing varieties of the disease emerged from acquiring the ColV plasmids, and that this process may have begun in livestock such as chickens and pigs. This study was published recently in Nature Communications.
“Zoonosis, particularly in relation to E. coli, should not be viewed simply as the transfer of a pathogen from an animal to a human. 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,” noted research co-author Steven Djordjevic.
Understanding the origins of pathogenic diseases can support proactive measures to prevent them from spreading, such as by using genome sequencing technology to predict pathogenic emergence and develop effective interventions, stated first author Cameron Reid. Similarly to the study, monitoring efforts following the “One Health” approach would focus on many potential sources ranging from domestic and wild animals, to food products, to environmental sources, recognizing how these sources interconnect in the evolution and spread of pathogens.