Condition category
Infections and Infestations
Date applied
Date assigned
Last edited
Prospectively registered
Overall trial status
Recruitment status

Plain English Summary

Background and study aims
Staphylococcus aureus (S. aureus) is a common bacterium with about one person in every three carrying it in their nose, or elsewhere on the skin. Some people carry it all the time, some only now and then, and others never carry it. Currently, we can’t explain why. For most people, carriage of 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. Understanding why only some people are carriers while others aren’t will help design new ways to prevent and treat such infections. The aim of this study is to investigate why some people carry S. aureus in their nose while others never do. The study will provide a better understanding of the biological, genetic and environmental factors that determine S. aureus carriage. One way to see if a person carries S. aureus is to analyse swabs taken from the nose. We are uncertain of the acceptability of collecting nasal swabs in large groups of volunteers. Therefore before we conduct a study in large numbers of people, we are doing two smaller studies to see if nasal self-swabbing is acceptable and feasible in large populations.

Who can participate?
Healthy volunteers who participated in the INTERVAL study

What does the study involve?
In stage 1, 250 participants are randomly allocated to one of two swabbing frequencies (two versus three swabs). The acceptability of each swabbing frequency is assessed based on participant response rates and participant feedback from an online questionnaire asking about experiences of taking part in the study.
In stage 2 a further 2000 participants are invited to collect nasal swabs. The number of swabs collected is informed by the results of stage 1 (i.e., either two or three). This stage assesses the feasibility of collecting, processing and analysing swabs from large numbers of participants.

What are the possible benefits and risks of participating?
We will not provide any new information or advice to participants based on the samples and data collected during the study; at present, this information has no clinical implications for the participant. As such, involvement in the study will have no direct benefit to participants. However, it is an opportunity for volunteers to support research, which addresses an important public health issue. There are no known risks associated with nasal swabbing. All participants will receive clear written instructions and a link to an online video demonstrating swabbing technique. Nasal swabbing may pose minor risks in individuals with nasal problems or nasal damage and, as such, potential participants who report having such conditions will be excluded from the study.

Where is the study run from?
The study is administered by the University of Cambridge and is conducted in the community across England.

When is the study starting and how long is it expected to run for?
September 2016 to June 2017

Who is funding the study?
University of Cambridge (UK)

Who is the main contact?
Dr Ewan Harrison

Trial website

Contact information



Primary contact

Dr Ewan Harrison


Contact details

Department of Medicine
University of Cambridge
Box 157
level 5
Addenbrooke's Hospital
Hills Road
United Kingdom

Additional identifiers

EudraCT number number

Protocol/serial number

Protocol version 1 - 15/06/2016

Study information

Scientific title

Understanding the biological basis of persistent carriage of Staphylococcus aureus in humans


Study hypothesis

The principal research question is to assess the feasibility and acceptability of protocols for the collection and processing of nasal self-swabs in healthy volunteers to inform a larger proposed study to investigate the biological basis of persistent Staphylococcus aureus (S. aureus) carriage.

The secondary research objectives are to assess:
1. The relative participant-acceptability of two vs three weekly nasal swabs
2. The prevalence of persistent S. aureus carriage rates in healthy volunteers
3. Lifestyle and biomarker correlates of persistent nasal carriage and validate associations with previously suggested candidate variants

Ethics approval

North West - Lancaster Research Ethics Committee, 27/06/2016, IREC reference: 16/NW/0507, RAS project ID: 202688

Study design

Two-stage feasibility study with interventional, observational and cross-sectional components

Primary study design


Secondary study design

Randomised controlled trial

Trial setting


Trial type


Patient information sheet

Not available in web format, please use contact details to request a participant information sheet


Nasal carriage of Staphylococcus aureus


Both stages of the study will involve the recruitment of participants who have taken part in a previous study (INTERVAL: ISRCTN24760606) and have agreed to be invited to other studies organised by NHS Blood and Transplant and/or University of Cambridge and/or University of Oxford.

In stage 1: Participant acceptability of collecting two versus three swabs will be compared in approximately 250 participants (125 per arm). Prior to invitation, there will be a 1:1 random allocation to each of the swabbing frequencies; simple block randomisation stratified by age and gender will be used. The acceptability of each protocol will be based on participant response rates to the two- and three-swab protocol and participant feedback from an online questionnaire asking about experiences of taking part in the study.

In Stage 2: A further (approximately) 2000 participants will be invited to collect nasal swabs. The number of swabs collected will be informed by the results of Stage 1 (i.e. either two or three). This stage will assess, more generally, the operational feasibility of collecting, processing and analysing swabs in large numbers of participants. It will also assess lifestyle and biomarker correlates of persistent nasal S. aureus carriage.

In both stages of the study prevalence rates of S. aureus carriage will be assessed.

Participants joining the study will be asked to complete an online baseline questionnaire designed to collect health and lifestyle information which may be relevant to predisposition to S. aureus carriage. On completion of their questionnaire, participants will be sent a nasal swabbing pack in the post and asked to return their first swab immediately and subsequent swabs at weekly intervals. Once participants have returned all swabs they will be sent an online feedback questionnaire about their experiences of taking the swabs and participating in the study.

The study will be administered by the University of Cambridge and will be conducted in the community across England.

Intervention type



Drug names

Primary outcome measures

Response rates to nasal swab collections including differences in response rates to initial invitation to provide two vs three swabs and compliance to the collection and return of two vs three swabs

Secondary outcome measures

Stages 1 & 2:
1. Participant feedback from the online questionnaire administered to participants on completion of their involvement in the study. Data collected will include binary (yes/no), Likert Scale and free text responses
2. Prevalence of persistent nasal carriage of Staphylococcus aureus in healthy volunteers. The point prevalence of carriage will be calculated using the first swabs returned by participants. Persistent carriage will be defined based on two positive swabs in participants randomised to the two-swab protocol and three positive swabs in participants randomised to the three-swab protocol.
3. Operational outcomes: the success of operational procedures will be reviewed including: posting of nasal swabbing packs, sample receipt at the processing laboratory and laboratory methods for sample processing and analysis

Stage 2:
Lifestyle, biomarker and genetic correlates of persistent S. aureus carriage assessed using either logistic or linear regression models

Overall trial start date


Overall trial end date


Reason abandoned


Participant inclusion criteria

1. Be already enrolled in the INTERVAL study
2. Have an email address for study participation
3. Reside in mainland England
4. Have a good understanding of the English language, both written and oral (study materials are not tailored to support non-English language speakers)

Participant type

Healthy volunteer

Age group




Target number of participants

Phase 1: 250, Phase 2: 2000

Participant exclusion criteria

1. Have received 3 invitations from the INTERVAL research study team to take part in other studies in the past year
2. Have withdrawn their consent to take part in the INTERVAL study
3. Have any abnormalities or ongoing medical conditions that affect the nose (e.g. nosebleeds, nasal polyps, rhinitis, etc)
4. Have undergone nasal surgery in the last year
5. Have had a nasal fracture in the last year
6. Are not going to be available to take part in the study during the next two months due to reasons such as an extended holiday

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

University of Cambridge
Department of Medicine Box 157, level 5 Addenbrooke's Hospital Hills Road
United Kingdom

Trial participating centre

University of Cambridge
Dept Public Health and Primary Care Strangeways Research Laboratory Worts Causeway
United Kingdom

Sponsor information


University of Cambridge (UK)

Sponsor details

School of Clinical Medicine
Addenbrooke's Hospital Hills Road
United Kingdom

Sponsor type




Funder type


Funder name

University of Cambridge (UK)

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

The findings from this study will be written up for publication in scientific journals and presentation to other researchers. In due course we will also provide details of the findings of the study on the CARRIAGE website.

Anonymous information and samples may be made available on request to researchers who have relevant scientific and ethics approvals for their planned research.

Intention to publish date


Participant level data

Available on request

Results - basic reporting

Publication summary

Publication citations

Additional files

Editorial Notes