A link between virulence and ecological abundance in natural populations of Staphylococcus aureus

Staphylococcus aureus is a major cause of severe infection in humans and ye t is carried without symptoms by a Large proportion of the population. We u sed multilocus sequence typing to characterize isolates of S. aureus recove red from asymptomatic nasal carriage and from episodes of severe disease wi thin a defined population. We identified a number of frequently carried gen otypes that were disproportionately common as causes of disease. even takin g into account their relative abundance among carriage isolates, The existe nce of these ecologically abundant hypervirulent clones suggests that facto rs promoting the ecological fitness of this important pathogen also increas e its virulence.