Defining the biological basis of Staphylococcus aureus carriage

Around one in five people carry *Staphylococcus aureus* bacteria permanently in their noses, yet no one knows why some people are carriers and others are not. This matters because carriers face a higher risk of serious *S. aureus* infections—ranging from skin abscesses to life-threatening sepsis—and the bacterium is a leading cause of hospital-acquired infections worldwide. The biological reasons for persistent carriage remain a black box, partly because previous studies have been too small or too narrow to untangle the many possible influences: a person’s genetic makeup, their immune system, the other microbes living in their nose, and lifestyle factors such as smoking or diet. The team will screen 25,000 healthy volunteers from two existing UK cohorts, sequence their nasal bacteria, and combine this with already-collected genome and lifestyle data. By running genome-wide association studies and other analyses, they aim to pinpoint which genetic variants, microbial species, and environmental factors determine whether someone becomes a long-term carrier. If successful, this fundamental science could reveal new targets for decolonisation therapies—for example, a probiotic nasal spray or a drug that blocks a host receptor the bacterium uses to stick to nasal cells. Reducing carriage rates in the population could lower infection risk for vulnerable patients, particularly those undergoing surgery or chemotherapy.