MRSA ‘superbug’ outbreak in hospital baby ward stopped by DNA sequencing


Scientists at the Wellcome Trust Sanger Institute, the University of Cambridge and Cambridge University Hospitals reported yesterday that a study being conducted on a new fast DNA-sequencing technology has helped stop a potentially deadly outbreak of the 'superbug' Methicillin-resistant Staphylococcus aureus (MRSA) in a baby ward.

"This is a dramatic demonstration that medical genomics is no longer a technology of the future — it is a technology of the here and now. By collaborating with NHS doctors, geneticists have shown that sequencing can have extremely important applications in healthcare today, halting an outbreak of a potentially deadly disease." said Sir Mark Walport, Director of the Wellcome Trust.

'Normal' Staphylococcus aureus exists in roughly 20 to 30 per cent of Canadians, as part of the normal 'flora' of our bodies (the bacteria that naturally inhabit us, either symbiotically or relatively harmless to us). MRSA is typically found in hospitals, where the antiseptic environment unfortunately tends to result in some bacteria developing drug resistances. MRSA is usually limited to skin infections, however it can complicate other illnesses a patient may be in the hospital for — especially if their illness or treatment weakens their immune system — which, in some cases, can result in death.

According to a presentation given by Andrew Simor at last year's Association of Medical and Microbial Infectious Disease (AMMI) Canada Conference in Montreal, this 'superbug' was involved in the deaths of 2200 Canadians in 2010, and cost an estimated $250 million in excess medical costs. Outbreaks in hospitals are a serious matter, and can close down entire wards to prevent its spread.

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The researchers were conducting a six-month study, using standard protocols to identify MRSA infections in 12 patients, and the new sequencing technology to identify the strains of the bacteria causing the infections. The new technology revealed that all the infections were due to the same strain, thus this was an outbreak, and it also revealed that the infection had spread further than they thought, as they found over twice as many people were infected with or carrying the same bacteria.

Additionally, while the study was being conducted, the infectious control team discovered that a newborn in the Special Care Baby Unit was carrying an MRSA bacteria, which the researchers were able to confirm as also being part of the outbreak, despite there being no apparent connection between the child and the other infected patients. The team screened 154 healthcare workers at the hospital, looking for anyone who may unknowingly be spreading the infection, and identified one person carrying MRSA. Another use of the fast-DNA sequencing technology quickly confirmed that this person was carrying the same strain as the others, and they were treated to prevent further spread.

"Our study highlights the power of advanced DNA sequencing used in real time to directly influence infection control procedures," says Dr Julian Parkhill, lead author of the study from the Wellcome Trust Sanger Institute. "There is a real health and cost burden from hospital outbreaks and significant benefits to be gained from their prevention and swift containment. This technology holds great promise for the quick and accurate identification of bacterial transmissions in our hospitals and could lead to a paradigm shift in how we manage infection control and practice."

According to Professor Sharon Peacock, lead author from the University of Cambridge and clinical specialist at the Health Protection Agency, this technology isn't ready for routine care until automated tools can be developed to interpret the DNA sequences and provide the information to healthcare workers in a useful way.

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"We are currently working on such a system." she said. "If we have a robust system of this type in operation when the outbreaks occur, we predict that we will be able to stop them after the first few cases, as we will rapidly find clear connections."