Using DNA analysis to track resistant E.coli around the world


A globally successful, antibiotic-resistant E. coli strain causing human infection – why and how has it spread?

Escherichia coli (E. coli) is a type or species of bacteria that is a common cause of infection in all age groups. It causes approximately four out of five urine infections in the UK, and around one in three bloodstream infections. Patients with infections requiring treatment are given antibiotics. However, the number of antibiotic-resistant E. coli causing infections has increased steadily over the last 20 years, making them more and more difficult for doctors to treat.

All living things, including E. coli, contain DNA, which is the genetic code that causes them to be structured and behave in the way that they do. Some closely genetically related E. coli (strains) share certain features, such as antibiotic resistance, and are more common causes of human infection than other strains. One of these common E. coli strains is known as ST131 (the “ST” part stands for “sequence type”).

As part of our research, we have analysed the complete genetic code, or “fingerprint”, of more than 200 isolates of ST131 E. coli from Asia, North America, Australasia and the UK, including some ST131 E. coli that are resistant to several different types, or classes, of antibiotic. We analyse the DNA/genetic code of bacteria using a technique known as “whole genome sequencing”, or WGS.


This has allowed us to work out that the widespread use of certain classes of antibiotic, known as cephalosporins and quinolones, following their introduction into clinical medicine in the late 1980s, is closely associated with the subsequent emergence and global spread of antibiotic-resistant ST131 E. coli.


Our study therefore highlights how important it is to use antibiotics as sensibly as possible, in order to try and limit how quickly antibiotic-resistant strains appear. It also demonstrates the value of being able to look at collections of bacterial strains from many different countries, and examine their complete DNA fingerprint. Antibiotic resistance in E. coli is a global problem, and we need to be able to work collaboratively in defining how it evolves, spreads and can be tackled.



-Original Paper “Evolutionary History of the Global Emergence of theEscherichia coli Epidemic Clone ST131″ –

–  This blog is by Nicole Stoesser, Clinical Research Fellow and Researcher at Modernising Medical Microbiology, who wrote the paper.

You can read about more of Nicole’s work here, and a list of her other publications are available here



Antibiotics – medicines that are used to treat infections caused by bacteria. These are grouped into different classes, depending on which parts of the bacteria they attack.

DNA – deoxyribonucleic acid – a molecule that stores the biological and structural information for all living things, including E. coli and you.

Antibiotic resistance – caused by changes in the DNA of bacteria that mean that certain types of antibiotic are no longer effective in killing these bacteria

Bacterial strain – a closely genetically related type of bacterium. This means that it has a very similar genetic “fingerprint” to other members of the same strain group.

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