Genetic changes tracked as bacteria become a fatal infection

An unusual case could tell researchers more about the genetic changes that occur when a common bacteria, normally carried without any problems, on rare occasions causes potentially life-threatening infections.

Eight mutations occurred in the common bacteria Staphylococcus aureus as it turned from an innocuous resident inside one person's nose into a fatal blood infection, an Oxford University study has found.

The study, which sequenced the complete DNA of the bacteria at regular time intervals, was able to identify for the first time the genetic changes that accompanied the transition to a dangerous infection.

Understanding the biological causes of serious bacterial infections could help guide screening in hospitals, and could inform efforts to develop vaccines against such infections. The study is published in the journal PNAS and was carried out in partnership with Oxford University Hospitals NHS Trust through the National Institute of Health Research (NIHR)Biomedical Research Centre, Oxford.

Professor Derrick Crook of the Nuffield Department of Clinical Medicine at Oxford University, one of the principal investigators, said: "Sequencing the whole bacterial genome was crucial to detecting these small changes in the DNA code. The genetic variation between bacterial samples was at much too low a level to be detected by conventional means.

"As DNA sequencing technology continues to get quicker and cheaper, this does point to a role for this technology in monitoring clinical samples for bacterial infections."

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