In England, Escherichia coli (E. coli) was isolated from patients with bloodstream infections showed that drug resistant 'superbugs' are not always out-competing with other strains, as some were found to be resistant to various antibiotics, reveals a new study which is the first large-scale genetic study . // Research by the Wellcome Trust Sanger Institute and their collaborators showed that new types of E. coli occur frequently, but unlike in some other infections, drug-resistant strains do not become a dominant cause of infection. The study was published in the Genome Research.
‘E. coli are the leading cause of bloodstream infections and there is an urgent need for new effective treatments against multidrug resistant strains.’
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The researchers found that infection was caused by more than 200 different types of E.coli. New strains including multidrug resistant E. coli were seen to emerge within the collection over time, but these quickly reached a balance with other strains in the population rather than increasing over time.Despite being a very common bacterium that is carried naturally in the human digestive tract, E. coli are also the leading cause of bloodstream infections. There were 35,676 cases in England in 2014, which often result from spread of infection from the urinary or gastrointestinal tract.
Certain strains of E. coli have been extensively studied, like the 'superbug' strain ST131 which is resistant to multiple antibiotics. But this study took a different approach - rather than just focusing on antibiotic-resistant strains, the study tapped into an unbiased collection of 1509 E. coli, the majority of which were from the British Society of Antimicrobial Chemotherapy Bacteraemia Surveillance programme collected over 11 years from across England. Using whole genome sequencing, the researchers discovered 228 different strains of E. coli in this collection.
The study captured the year (2002) in which ST131 emerged in England. Within a short space of time, the number of ST131 isolates reached an equilibrium with other types. Around the same time, another type (ST69, not a multidrug resistant strain) also emerged, and again quickly reached an equilibrium within the overall population.
Prof Sharon Peacock, from the Wellcome Trust Sanger Institute and London School of Hygiene & Tropical Medicine*, said: "These findings suggest that the emergence of new types of E. coli is not uncommon, and is necessarily followed by successful competition with other types to become a dominant cause of infection in humans. The reason for this equilibrium may relate to the fact that all bacteria are constantly competing with others to survive in places where they are carried, such as the gut."
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Dr Julian Parkhill, from the Sanger Institute, said: "Our study indicates that there are many reasons for the success of different strains of E. coli, and these include competition between bacteria, as well as interaction with the human host and antibiotic resistance. This suggests that the ultimate source of E. coli causing bloodstream infections is the diverse bacterial population in the wider community."
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Tim Jinks, Head of Drug-Resistant Infections at Wellcome, said: "E. coli are the leading cause of bloodstream infections and this study helps illustrate the incredible complexity of the acquisition and spread of multidrug-resistant strains. Finding new effective treatments against multidrug resistant strains remains an important priority."
Source-Eurekalert