Tracking Bacterial Transmission: A New Frontier in Public Health

For the first time, researchers from the Wellcome Sanger Institute, the University of Oslo, the University of Helsinki, and Aalto University in Finland, in collaboration with their colleagues, have estimated the efficiency of gut bacteria transmission from person to person. Previously, such calculations, which measure transmission rates, were primarily possible for viruses.

Tracing Dangerous Strains Across Populations

The study, published in Nature Communications, examined three major strains of E. coli bacteria prevalent in the UK and Norway. Two of these strains are resistant to multiple classes of antibiotics and are also the most common causes of urinary tract and bloodstream infections in both countries. Researchers suggest that improving surveillance of these strains could guide public health responses and help prevent outbreaks of hard-to-treat infections.

In the long term, understanding the genetic factors that aid the spread of E. coli bacteria could lead to more targeted treatments and reduce reliance on broad-spectrum antibiotics. The approach used in this study can be adapted to investigate other bacterial pathogens and improve strategies for managing invasive infections.

Applying Viral Transmission Metrics to Bacteria

Scientists typically describe the infectiousness of a pathogen using the basic reproduction number, known as R0. This number estimates how many new cases one infected individual might cause. It is usually applied to viruses and helps predict whether an outbreak will expand or decline. Until now, researchers have been unable to determine an R0 value for bacteria that typically colonize the gut, as they often live in the body without causing disease.

To overcome this challenge, the team combined data from the UK Baby Biome Study with genomic information from E. coli bloodstream infection surveillance programs in the UK and Norway.

Understanding the R0 Value for Bacteria

Assigning an R0 value to bacteria opens the door to a clearer understanding of how bacterial infections spread. It also helps identify which strains pose the greatest threat and can guide public health strategies to better protect individuals with weakened immune systems.

Fanny Aujala, co-first author from Aalto University in Finland, explained, “With a large amount of systematically collected data, it was possible to build a simulation model to predict the R0 for E. coli bacteria. To our knowledge, this was the first time not only for E. coli but for any bacteria living in our gut microbiome.”

A New Lens on Bacterial Genetics

Professor Jukka Corander, lead author at the Wellcome Sanger Institute and the University of Oslo, added, “Having an R0 for E. coli allows us to see the spread of bacteria across populations more clearly and compare this to other infections. Now that we can see how quickly some of these bacterial strains spread, it is crucial to understand their genetic drivers.”

Conclusion

This research represents a significant step forward in improving our understanding of bacterial transmission, especially those resistant to antibiotics. By determining the R0 value for E. coli strains, we can now better assess the threat level of these strains and direct public health efforts to protect the most vulnerable groups. This approach is not limited to E. coli but can extend to other pathogens, providing a powerful tool in combating the spread of bacterial infections.