PNAS paper on staphylococcal evolution during infection

Today in PNAS Early Edition my colleagues and I have a paper published reporting the genome evolution of Staphylococcus aureus during the transition from prolonged nasal carriage to invasive disease. Since Staph. aureus, a major bacterial cause of life-threatening infections, is carried without symptoms by a quarter of healthy adults, a natural question is to ask what genetic changes - if any - accompany the transition to invasive disease. The opportunity to pursue this question arose from a detailed epidemiological investigation of asymptomatic Staph. aureus nasal carriage set up by colleagues of mine including Derrick Crook and Kyle Knox. The study has recruited over 1,000 participants in Oxfordshire since it began running in October 2008. One participant developed a bloodstream infection that was indistinguishable from the strain of Staph. aureus persistently carried in the nose for the previous 13 months. Members of the Modernising Medical Microbiology consortium, led by Derrick and Rory Bowden, sequenced the genomes of 68 bacterial colonies isolated from the nasal and blood samples from this participant, and 101 colonies from nasal samples from two other participants that did not go on to develop disease. Bernadette Young and Tanya Golubchik analyzed the genome evolution of these bacterial populations, discovering an unusual pattern in the mutations that occurred between nasal carriage and invasive disease: mutations that led to prematurely truncated proteins were significantly over-represented, including one in a gene previously associated with virulence in bacteria. To know more, read the full open access article.