Åsa Sjöling et al publish about the global spread of enterotoxin-producing E. coli (ETEC) in Nature Genetics

Genetically related ETEC have spread globally and over time

Enterotoxigenic Escherichia coli (ETEC) bacteria are a major cause of diarrhoea in children below five years of age in low and middle-income countries and also in travellers. A group of researchers lead by Ann-Mari Svennerholm and Åsa Sjöling at University of Gothenburg, and Karolinska Institutet and Gordon Dougan at the Wellcome Trust Sanger Institute and with first author PhD student Astrid von Mentzer, have now conducted a study analysing the genetic composition of ETEC, which is the first large-scale whole-genome sequencing project on a global collection of ETEC. They found that several distinct and stable clusters (lineages) of ETEC with specific virulence determinants have spread worldwide.

ETEC is estimated to cause diarrhoea in at least 400 million people and cause up to 400,000 deaths each year. This publication describes that ETEC isolates that were collected in Asia, Africa and the Americas during the last 30 years constitute distinct genetically closely related lineages that share specific toxin profiles, O antigens and colonization factors. The researchers could show that several major ETEC lineages with specific virulence profiles have emerged between 51 to 174 years ago. The close genetic relationship within the lineages indicates that the virulence genes were acquired once in one bacterium and then spread globally.

Although ETEC is a highly diverse pathogen and previously thought to randomly acquire virulence genes, these findings suggest a specific link between the chromosomal background and plasmids encoding such genes. This changes the perception of how new ETEC strains arise.

The results of the study also support that the same ETEC lineages may infect children and adults, as well as travellers in widely different geographic areas. 

Since ETEC with the same virulence factor profiles are related and globally present this study supports the strategy taken to develop a vaccine expressing the most prevalent colonization factors in combination with a toxin antigen. The results may also allow identification of additional prevalent vaccine targets.

Ultimately, these findings have shed light on how bacterial pathogens may develop and spread and the researchers hope that this will result in development of better interventions to fight emerging bacterial diseases.

Read the Article "Identification of enterotoxigenic Escherichia coli (ETEC) clades with long-term global distribution" in Nature Genetics