Rapid whole-genome sequencing ends MRSA outbreak

Researchers isolate the MRSA strain and track it to a staff member unwittingly carrying the bacteria

Rapid whole-genome sequencing helped a hospital isolate a MRSA outbreak and track new infections to a single staff member, according to an article published Wednesday in The Lancet Infectious Diseases journal.

It was the first time DNA sequencing had been used to help end an infectious disease outbreak, according to an announcement by Cambridge University, which participated in the study.

The 2011 outbreak in a special care baby unit in the U.K. affected 12 infants over six months, but without DNA sequencing of the bacteria authorities could not confirm they were linked. Whole-genome sequencing identified 26 related cases, with transmission occurring not just among babies, but between the babies' mothers, their partners, and other members of the community, according to the Lancet article.

The sequencing also confirmed that a new MRSA case two months later was linked to the original outbreak, the Cambridge announcement noted, indicating an ongoing source of infection. With further testing, researchers tracked down a staff member who was carrying the germ for the antibiotic-resistant staph bacteria, continuing to spread the germ even after a deep clean of the baby unit.

The study showed that whole-genome sequencing "holds great promise for rapid, accurate, and comprehensive identification of bacterial transmission pathways in hospital and community settings, with concomitant reductions in infections, morbidity, and costs," the researchers concluded.

They noted that containing the outbreak and treating the patients cost at least $16,000, while the cost of rapid whole-genome sequencing of one MRSA isolate is about $150.

"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," researcher Julian Parkhill, head of the pathogen sequencing unit at Britain's Wellcome Trust Sanger Institute, said in the Cambridge announcement.

Lead author Sharon Peacock, a Cambridge professor and clinical specialist at Britain's Health Protection Agency, said automated tools to interpret sequence data will be needed before rapid whole-genome sequencing can routinely be used to quickly identify MRSA and other bacterial outbreaks such as e. coli or tuberculosis.

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

To learn more:
- here's the Lancet article
- read the related announcement

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