November 14, 2012
Researchers Put An End To MRSA Superbug After Successful Genome Sequencing
Lawrence LeBlond for redOrbit.com - Your Universe Online
Methicillin-resistant Staphylococcus aureus (MRSA), a dangerous staph infection often associated with medical procedures in hospitals and doctor´s offices, has had its genome sequenced by UK researchers.
The sequencing was completed by researchers at Wellcome Trust Sanger Institute, the University of Cambridge and Cambridge University Hospitals. Using the advanced DNA sequencing technology they were able to confirm the presence of an ongoing outbreak of MRSA in real time. Their efforts led to the stoppage of the outbreak, saving countless patients from further harm. While other methods have been used to track down hospital infection outbreaks, this new method is by far the fastest and most accurate.
The researchers discovered the outbreak had extended into the wider community, which also could not have been reached using previous methods. The new technologies also led the team to link the outbreak to an unsuspecting carrier, who was treated to eradicate the infection.
"We are always seeking ways to improve our patient care and wanted to explore the role that the latest sequencing technologies could play in the control of infections in hospitals," Dr. Nick Brown, consultant microbiologist at the Health Protection Agency and infection control doctor at Addenbrooke's Hospital Cambridge, said in a statement.
"What we have glimpsed through this pioneering study is a future in which new sequencing methods will help us to identify, manage and stop hospital outbreaks and deliver even better patient care,” added Brown.
Doctors were concerned when they started detecting MRSA in babies at Rosie Hospital in Cambridge. In all, doctors found infections in 12 babies at the facility´s maternity ward during routine screening. But their testing could not give them a clear picture if the infection was from a single outbreak or if separate cases were being brought into the hospital.
With no other alternatives, doctors turned to science for an answer.
In their study, the researchers analyzed MRSA isolates in the 12 babies with DNA sequencing technology and demonstrated clearly that all the MRSA bacteria were closely related, indicating there was an official outbreak. Their study also showed the outbreak was more extensive than previously realized, discovering that more than twice as many people were carrying or were infected with the same strain. Many of these additional cases were people who had recent links to the hospital but were otherwise healthy and living in the community when they developed a MRSA infection.
During the sequencing, the infection control team identified a new case of MRSA in the Special Care Baby Unit at the hospital, occurring 64 days after the last MRSA-positive patient had left the same unit. The team found that this strain was also part of the outbreak, despite the lack of apparent links between the new case and previous ones. This gave researchers the idea to look for a possible individual who was unknowingly carrying and transmitting the infectious strain.
After screening 154 healthcare workers for MRSA the team was able to single out the one staff member who was carrying the MRSA. Using the DNA sequencing, they confirmed that this person was carrying the MRSA strain linked to the outbreak. The team quickly treated the worker to eradicate the MRSA strain and remove the risk permanently.
"Our study highlights the power of advanced DNA sequencing used in real time to directly influence infection control procedures," said Dr Julian Parkhill, lead author from the Wellcome Trust Sanger Institute.
"Our study indicates the considerable potential of sequencing for the rapid identification of MRSA outbreaks," added Professor Sharon Peacock, lead author from the University of Cambridge and clinical specialist at the Health Protection Agency. "What we need before this can be introduced into routine care is automated tools that interpret sequence data and provide readily understandable information to healthcare workers. We are currently working on such a system."
Researchers have already come a long way in DNA sequencing of entire genetic codes. What once cost millions of dollars can now be performed for a fraction of that. Not only has the cost been slashed, but the time has fallen dramatically as well, dropping from months to just hours.
Dr Parkhill said it could get even cheaper: "People are talking about the thousand dollar human genome“¦If you can do the human genome for a thousand dollars you can do a bacterial genome for one dollar."
“The study clearly highlights the power of whole genome sequencing for resolving the source and the spread of an epidemic of hospital acquired infection such as MRSA,” Prof Ross Fitzgerald, from the Roslin Institute at the University of Edinburgh, told the BBC's James Gallagher.
“It will ultimately, within a small number of years, be standard practice for any hospital outbreak,” said Fitzgerald, who was not involved in the study. “I fully expect this to be rolled out as a standard approach in UK hospitals in the very near future.”
MRSA kills an estimated 19,000 people in the US every year. Although infection rates have declined significantly throughout Britain in recent years, it is still a major threat with several hundred deaths per year. The bug is present in nearly one percent of the population at any time, yet it does not always cause infection.
The study was published in the medical journal Lancet Infectious Diseases.