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Genetic code changes may help track global, local strains of MRSA infections
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Investigators at 10 international centers have used a new strategy to show how transmission of methicillin-resistant Staphylococcus aureus from one person to another can be precisely tracked in a hospital setting and on a larger global scale.
Tracking strains this way may help provide a better understanding of how they spread and evolve, possibly leading to new infection control strategies, according to a press release from the Wellcome Trust Sanger Institute.
Using a high-throughput DNA sequencing technology, the investigators could zoom in on differences in the genetic code among individuals worldwide who developed methicillin-resistant Staphylococcus aureus (MRSA) infections from either a person-to-person infection at the single-hospital level or large-scale transmission events.
The study appears in Science.
Two sets of samples
Lead author Simon R. Harris, PhD, of the Wellcome Trust Sanger Institute in Cambridge, United Kingdom, and colleagues from Portugal, Thailand and the United States compared the individual MRSA isolates from two sets of samples to determine their genetic relatedness. One set contained 42 MRSA samples taken worldwide between 1982 and 2003. The second set of 20 samples came from “patients who developed MRSA infection within 7 months of each other, all possibly linked by a chain or person-to-person transmission,” Harris noted in the press release.
The new method enabled the team to identify single-letter changes of the genetic codes in the genetic codes and spot differences between related MRSA isolates.
Related strains
The investigators discovered the actual rates of DNA sequence mutation, including one strain that acquired nearly one single-letter change every 6 weeks. They also found that related strains caused the infection in patients in the same intensive care unit in adjacent blocks of one hospital. However, the investigators found that strains identified in patients housed elsewhere at the same hospital were much less similar to each other.
“The new method has allowed us to gain insights into the fundamental processes of evolution in S. aureus, one of the most important bacterial pathogens in health care in the world,” Sharon Peacock, MDPhD, MRCP, MRCPath, an author of the study stated in the release. “We are now able to discriminate between one strain and another, even where they are very closely related. Our research should inform global surveillance strategies to track the spread of MRSA.”
The investigators noted that their research reaches beyond MRSA and has the possibility to underpin future studies into the transmission and evolution of other bacteria posing a significant health burden.
For more information:
Harris SR, Feil EJ, Holden MT, et al. .Evolution of MRSA during hospital transmission and intercontinental spread. Science. 2010. 327(5964):469-474.
Research support was obtained from grants from Fundação para a Ciência a Tecnologia, Guy’s and St. Thomas’ Charity; and the Department of Health via the NIHR comprehensive Biomedical Research Centre award to Guy’s & St. Thomas’ NHS Foundation Trust in partnership with King’s College London.
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