What is the study about?
We examined the DNA of a particular type of multidrug resistant E. coli called ST131. This type of bacteria was relatively unheard of until about 5 years ago but is now one of the most common causes of urinary tract and bloodstream infections. We were able to track the global emergence of ST131 by analysing a collection of isolates from all over the world. We found that they all evolved from a common ancestor quite recently and were resistant to multiple antibiotics.
Why is it important?
Urinary tract infections affect more than 150 million people around the world every year and about 50% of all women experience a urinary tract infection in their lifetime. ST131 are resistant to most antibiotics commonly used to treat urinary tract infections so it is important to be able to identify this type of E. coli early and treat the infection with an antibiotic that will work. Carbapenems are one of the few remaining types of antibiotics that are effective in treating ST131 but resistance to this antibiotic is increasing.
What should we be worried about?
Carbapenem resistance is an emerging problem, as the gene responsible is able to be easily transferred between bacteria. In the last couple of years carbapenem resistance genes have been reported in a small number of ST131 bacteria. The concern is that this gene will spread throughout the ST131 population, which is already the most successful *E. coli* clone to date. Not only would this limit treatment options for ST131 even further, it would also increase the chances that these resistance genes would be passed to other types of pathogenic bacteria.
How does our study help?
Our study provides a framework for understanding how these bacteria
have evolved and spread around the globe. The genetic data that we
produced can be used to develop new screening methods to ensure that
ST131 are identified early in patients so that the best antibiotic
treatment can be used. Ongoing surveillance of ST131 will also be
important for tracking increased antibiotic resistance in this type of
E. coli. In the longer term this work gives us the opportunity to
develop new vaccines or therapies for preventing ST131. The fact that
all ST131 are descended from a single ancestor means they may share an
Achilles’ heel that we can target.
How did we do the study?
We collected ST131 isolates from around the world from the year 2000 to 2011. We used “next generation” DNA sequencing to determine the genome of each isolate – the genome is the collection of all genes in an organism. Each E. coli has about 5000 genes, so we studied about half a million genes using bioinformatics, a discipline that merges biology and computing. The software that we developed to do this analysis and the data that we produced are now freely available to the rest of the scientific community.
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