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UK team tracks evolution of MRSA

25 January 2010
Appeared in BioNews 542

For the first time, a Cambridge-led team of scientists has succeeded in tracking the evolution and transmission of methicillin resistant staphylococcus aureus (MRSA) across the world, offering the possibility of affordable tests to identify and block fatal superbugs before they spread. The breakthrough, led by the Wellcome Trust Sanger Institute (WTSI) in Hinxton, Cambridgeshire, UK, and published in the journal Science, means that researchers and public health officials may be better able to understand and control the spread of bacteria around the world, and from person to person.

In the study, the team examined 63 isolates of one MRSA strain, called ST239, from two different samples: 43 from a global strain that infected people between 1982 and 2003, and 20 from a hospital in Thailand where the patients developed MRSA infection within seven months of each other, possibly due to transmission from person to person. The samples were selected to test whether the team's method - a high-throughput genomics approach that allows a high-resolution view of the smallest genetic mutations in the bacteria's DNA - could successfully track infection on both a global and an individual scale. The success of the new technique relies on the use of full genomes rather than small sections of DNA, which allowed the team to see single-letter genetic changes in the samples, and to construct a genetic 'family tree' of the MRSA microbes as a result. In addition, they were able to calculate the rate of mutations in the DNA sequence - about one single-letter change every six weeks - an unprecedented insight into the rate of bacterial evolution in vivo.

In the global sample, the team found that the isolates from Europe were at the base of the evolutionary tree, suggesting that the origins of MRSA are related to the introduction of widespread antibiotic use in Europe in the 1960s. In the Thai sample, the team found that two different groups of isolates had been introduced to the hospital separately, and that of 20 infections, only five were caused by the same bacteria.

The implications of the study for public health were pointed out by Dr Sharon Peacock from Cambridge University: 'this technology represents the potential to trace transmission pathways of MRSA more definitively so that interventions or treatments can be targeted with precision and according to need.'

However, the team highlighted that the costs associated with sequencing the full genome of an organism are an important limitation on it's widespread use, and the technique still needs refining before it can be cheaply used by the state-funded NHS. Nonetheless, as senior author Dr Stephen Bentley points out: 'ten years ago it took about three years and cost about half a million pounds…now it takes between four and six weeks, and costs about £200… Perhaps if you can get the cost of an individual test down to £20 or £30 then it may be viable to introduce that into a hospital setting as a routine test.'

Antibiotics 'may have spawned MRSA'
Press Association |  22 January 2010
DNA boosts fight to beat deadly bug
The Mirror |  22 January 2010
Evolution of MRSA During Hospital Transmission and Intercontinental Spread
Science |  22 January 2010
Gene sleuthing tracks variation in MRSA superbug
Washington Post |  21 January 2010
Genetics Used to Track Transmission of MRSA Bacteria
Business Week |  21 January 2010
Research-sleuths succeed in tracking MRSA super-bacteria
AFP |  22 January 2010
The tracker that could head off hospital bugs
The Independent |  21 January 2010
Tracking MRSA Evolution and Transmission: Revolutionary Strategy for Control and Prevention of Infection
ScienceDaily |  22 January 2010
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An outbreak of a drug-resistant bacterial bug, which killed six people and infected 11 more, was stopped partially thanks to genome sequencing, a paper in Science Translational Medicine reports...
21 May 2012 - by James Brooks 
The emergence and spread of MRSA in the UK has been tracked thanks to genetic analysis of samples taken from infected patients over a 53-year period. The study, published in the journal PNAS, suggests that hospitals in large cities act as breeding grounds for new, increasingly resistant MRSA variants...
30 April 2012 - by Dr Victoria Burchell 
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13 June 2011 - by Dr Gabrielle Samuel 
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8 March 2010 - by Seil Collins 
Scientists have catalogued the genes of microbes living in our gut, information that could be crucial in assessing the impact of microbes on our health. The study, published in Nature, reports the sequencing of 3.3 million microbial genes, a gene set 150 times larger than the human genome....
10 January 2010 - by Sarah Pritchard 
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Scientists have announced that hospital 'superbugs', bacteria resistant to antibiotics, have been dealt a blow by the decoding of the genomes of two of the most feared of the bugs. Japanese researchers from Juntendo University in Tokyo have decoded the DNA sequence of two antibiotic-resistant strains of the bacteria staphylococcus...
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