* Bacterial DNA sequences used to map MRSA outbreak
* Real-time analysis helped identify source, stop spread
* Technique could be used to control spread of other bugs
By Kate Kelland
LONDON, Nov 14 (Reuters) – Researchers have used DNA
sequencing for the first time to identify, analyse and put a
halt to an infectious disease outbreak in a hospital.
The success of the technique, which used fast genome
sequencing technology to control an outbreak of the MRSA
superbug on a baby ward, suggests it could be used to control
hospital bugs, salmonella and E.coli infections and diseases
like tuberculosis, scientists said.
“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,” said Nick Brown, an
infection control doctor at Addenbrooke’s Hospital Cambridge,
who co-led the study and presented the findings at a briefing.
MRSA, or methicillin-resistant staphylococcus aureus, is a
drug-resistant bacterial infection, or superbug, and a serious
public health problem. When outbreaks occur in hospitals it can
lead to the closure of whole wards with many people infected.
The bug kills an estimated 19,000 people in the United
States per year. Although rates of MRSA infection have come down
significantly in Britain in recent years, it still presents a
major threat with several hundred deaths a year and high
hospital costs involved in managing infected patients.
Julian Parkhill from Britain’s Sanger Institute, who also
worked on the study, said there is a “real health and cost
burden from hospital outbreaks” which could be significantly
reduced or eliminated if they were contained swiftly.
In the study, staff at Addenbrooke’s hospital using routine
screening over a six month period found 12 patients carrying
MRSA. Because they were only using standard tests, which provide
limited information, the infection control team was not able to
tell if the 12 were part of an outbreak, or were unconnected
cases that did not present a threat.
MRSA is a bug present in around one percent of the
population at any time, and does not always cause infection.
Parkhill and Brown’s team analysed MRSA samples from the 12
patients with DNA sequencing technology and found that all the
MRSA bacteria were closely related, confirming an outbreak.
By tracing relatives and other people who had recent links
to the hospital, they also found the outbreak was more extensive
than previously thought, with twice as many people carrying or
infected with the MRSA strain.
While this sequencing study was underway, the hospital’s
infection control team found a MRSA case in the special care
baby unit – 64 days after the last MRSA patient had left.
The team used advanced DNA sequencing to show in real time
that this strain was also part of the same outbreak, raising the
possibility that a staff member was unknowingly carrying and
transmitting the MRSA strain.
After screening 154 staff they found one carrying MRSA and,
using DNA sequencing, confirmed it was the strain linked to the
outbreak. The worker was quickly treated to eradicate the bug,
and any further spread was stopped.
The researchers, whose findings were published in the Lancet
Infectious Diseases journal, say this kind of fast genome
sequencing could eventually form the basis for regional or
national infection surveillance programmes designed to nip
infectious disease outbreaks in the bud.
“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,” said Parkhill.
It could also be used for outbreaks of food-borne infections
like salmonella or E.coli. Genome sequencing was used in an
E.coli outbreak in Europe in 2011, but only in the latter stages
to help identify the source.
(Reporting by Kate Kelland; Editing by Rosalind Russell)
