CARRIAGE study: Understanding the biological basis of persistent carriage of Staphylococcus aureus in humans

Study code

Lead researcher
Dr Ewan Harrison

Study type
Participant re-contact

Institution or company
Welcome Sanger Institute

Researcher type

Speciality area

Recruitment Site


20% of adult humans are persistently colonised in the nose by the bacterium Staphylococcus aureus (S. aureus) . For most people, being colonised by S. aureus is harmless. However, a small number of people are susceptible to S. aureus infections due to a weakened immune system and, in some cases, these infections may be serious and resistant to antibiotic treatment. 

The aim of the CARRIAGE study is to investigate why some people carry S. aureus in their nose while others never do. S. aureus is a common bacterium with about one person in every three carrying it in their nose, or elsewhere on the skin. The research will provide a better understanding of the biological, genetic and environmental determinants of S. aureus carriage.

The gold standard method to detect if a person is carrier of S. aureus is by analysing nasal swabs. If you decide to join and consent to join the study we will ask you to fill in a short (10-minute) online questionnaire which will ask for health and lifestyle information and then we will send you a CARRIAGE study ‘participant pack’ by post to your house.

We will ask you to take a nasal swab once a week for three weeks and post the swabs back to our laboratory using the FREEPOST bags that we will provide.

The lab will be able to analyse these samples and find out if you are a persistent carrier (3 S. aureus  positive swabs), intermittent carrier (1 or 2 S. aureus positive swabs) or a non-carrier (3 negative S. aureus swabs). 

Once you have returned your swabs, we will ask you to fill in a further short (5-minute) questionnaire to provide us with some feedback on how you found taking part in the study and how we might improve things.

For a subset of the swabs, we will identify what other bacterial species are present by extracting the DNA from the bacteria one the swabs and sequencing it. 

We will then combine the results from the nasal swabs with the questionnaire, electronic health record data and human genetics data already available for participants. This will enable analysis that will seek to understand what human factors contribute if an individual is colonised by S. aureus or not.