E. coli strain nears complete resistance

The genome sequencing of a multidrug-resistant strain of Escherichia coli, E. coli sequence type 131 (ST131), suggests it is only one gene away from being resistant to almost all antibiotics.

This pathogenic bacterium is responsible for a high proportion of extra intestinal infections, such as urinary tract and blood stream infections.

Researchers involved in the collaborative study analysed the molecular epidemiology of a collection of E. coli ST131 strains isolated from six distinct geographical locations around the world between 2000 and 2011.

Dr Nouri Ben Zakour from the Australian Infectious Diseases Research Centre at the University of Queensland said E. coli ST131 was not considered to be problematic five years ago.

“This study lets us understand in detail the evolution of a bacterial pathogen from obscurity to notoriety,” she said.

E. coli ST131 arose from a single common ancestor prior to 2000 largely as a result of genetic recombination.

Its rapid emergence and successful spread is strongly associated with several factors, including resistance to multiple antibiotics, such as fluoroquinolone and ceftazidime (via the production of CTX-M-15 extended spectrum β-lactamase), and a high virulence gene content.

“More than 150 million cases of urinary tract infection are reported globally every year, so an E. coli resistant to all currently effective antibiotic treatments could be devastating to the community,” said Dr Ben Zakour, emphasising that urinary tract and bloodstream infections could become more common and difficult to treat.

The research team used the latest DNA sequencing techniques to identify the genetic differences between E. coli ST131 strains taken from six regions around the world.

“We needed to develop new software just to analyse all of the data,” Dr Ben Zakour said.

Senior researcher Dr Scott Beatson said it was vitally important to understand E. coli ST131, particularly because there were few new antimicrobial drugs in the developmental pipeline.

“The gravity of this problem is such that E. coli ST131 are only one gene away from being resistant to all antibiotics that can be used to effectively treat urinary tract infections,” he said.

Co-first author Dr Nicola Petty, who now leads a research group in the ithree infection, immunity and innovation institute at the University of Technology Sydney, said the research would enable the development of tests to rapidly detect and help combat the spread of this superbug.

The study was published in the Proceedings of the National Academy of Sciences USA.