Pathogenic strains of E. coli emerge by acquiring genetic material

New study suggests harmless E.coli acquired new genetic material in a wide range of hosts, including poultry and pigs, to become a multidrug-resistant pathogen strain in humans.

More E.coli strains inhabit the digestive tracts of mammalian and avian hosts as harmless residents (commensals). When E.coli acquire genes that allow them to survive in niches other than the gut in humans, they can cause disease. Extra-intestinal pathogen E.coli (ExPEC) is the leading cause of urinary tract infections (UTIs) and the second most common cause of neonatal meningitis. It also causes sepsis which kills nearly 11 million people each year.

ST58 is an unusual ExPEC strain that is increasingly responsible for sporadic and persistent bloodstream infections worldwide. Its proportion in bacteremia has more than doubled over the past 12 years, shows a study carried out on patients in Paris and the Paris region. In addition to infecting humans, multidrug-resistant ST58 is found in farm animals such as cattle, poultry, pigs, as well as in flies, manure, soil, and water.

It is unclear how ST58 emerged as a human pathogen. It is particularly unusual because ST58 belongs to phylogroup B1, one of eight groups in which E.coli are classified, i.e. rarely pathogenic.

In a new study published in the journal Communication Nature (“A role for ColV plasmids in the evolution of pathogenic Escherichia coli ST58”), Cameron Reid, PhD, University of Technology Sydney, and his team performed a pan-genomic epidemiological analysis of 752 ST58 strains isolated from humans , animal, and environmental sources worldwide to better understand the evolution and genomic characteristics of this emerging pathogenic strain that is a growing cause of urinary tract infections and sepsis.

“We found that E.coli ST58 from pigs, cattle and chickens contains pieces of genetic material called ColV plasmids, which are characteristic of this strain of pathogens. E.coli“, said Reid. ColV plasmids – circular double-stranded DNA molecules that replicate independently of the bacterial chromosome – are widespread among avian pathogens. E.coli (APEC) and cause colisepticaemia in birds. Acquisition of ColV plasmids can prime harmless strains of E.coli cause extra-intestinal infections in humans and increase their resistance to antimicrobials.

“Zonoses, particularly in relation to E.coli, should not be viewed simply as the transfer of a pathogen from an animal to a human,” said Steven Djordjevic, PhD, professor of infectious diseases, group leader at the iThree Institute at the University of Technology in Sydney and lead author of the study. . “It should rather be understood as a complex phenomenon resulting from a vast network of interactions between groups of E.coli and other bacteria, and the selective pressures they encounter in humans and animals.

The authors noted that their results indicate that acquisition of ColV plasmids and non-human sources such as cattle, chickens and pigs played a role in the evolution of ST58 as a human pathogen. “The contribution of non-human sources to infectious disease in humans is generally poorly understood and its potential importance underestimated, as evidenced by the debate regarding the ecological origins of the SARS-CoV2 virus,” Reid said.

The study has broad implications for public health policy that span across the food industry and veterinary and clinical settings. “In a globalized world, acutely susceptible to the rapid spread of pathogens, the importance of proactive management of microbial threats to public health cannot be underestimated,” said Reid. “To date, infectious disease public health has been a reactive discipline, where action can only be taken after a pathogen has emerged and caused harm.”

Reid hopes genome sequencing technology will enable public health policy to take a more proactive stance on infectious disease by predicting the emergence of pathogens through genome monitoring and implementing interventions. preventive. Reid said this requires ongoing research and collaborations with government, public health agencies, food producers and clinicians, and would involve monitoring non-human sources of microbes.

“This would include domestic and wild animals, especially birds, food products, sewers and waterways, in what is called a ‘One Health’ approach. Certain microbes, such as ST58 E.coliexperience very few barriers between these increasingly interconnected hosts and environments,” said Reid.

The authors emphasized that pathogen emergence must be understood within a One Health framework, where pathogen evolution is analyzed in the context of complex mechanistic factors and interactions between environments and hosts rather than in historically ineffective human-centered approaches.

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