A landmark study published in Nature Communications shows that people who carry Staphylococcus aureus (S. aureus) persistently in their nose have fewer bacterial species overall. In contrast, certain nasal bacteria appear to protect against S. aureus colonization. This is the largest investigation of the nasal microbiome to date, involving more than 1,000 healthy blood donors.
Why S. aureus Matters
S. aureus lives harmlessly in the noses of nearly 30% of people. However, when it enters the body through wounds, surgical sites, or cuts, it can cause life-threatening infections. Globally, S. aureus infections are the second leading cause of bacterial infection–related deaths after tuberculosis, accounting for nearly one million deaths each year. Antibiotic-resistant strains such as MRSA make treatment even more challenging.
Historically, individuals have been classified as persistent carriers, intermittent carriers, or non-carriers. Because S. aureus carriage significantly increases the risk of post-operative infections, hospitals often screen patients undergoing procedures like joint replacements.
Study Design and Methodology
To better understand how nasal bacteria influence S. aureus colonization, researchers from the Wellcome Sanger Institute, University of Cambridge, Imperial College London, and collaborators collected three weekly nasal swabs from 1,100 adults across England.
As reported by medicalxpress, the team used standard culture tests to detect S. aureus and performed DNA sequencing to identify bacterial species present in each sample. They then applied advanced statistical methods and machine-learning tools to identify patterns within the nasal microbiome and predict carrier status.
Key Findings
The study revealed two major insights:
- Persistent carriers have a distinct nasal microbiome.
Their nasal samples showed high levels of S. aureus but fewer other bacterial species. This reduced diversity suggests that S. aureus may dominate and outcompete other bacteria in persistent carriers. - Certain bacteria may protect against S. aureus.
Non-carriers frequently had species such as S. epidermidis, Dolosigranulum pigrum, and Moraxella catarrhalis, which were less common in persistent carriers. These bacteria may help resist S. aureus colonization.
Using machine learning, the researchers accurately predicted persistent carriers based on the nasal bacterial profile. Notably, they propose that “intermittent carriers” may not represent a true biological group—these individuals are likely non-carriers who temporarily picked up S. aureus after exposure.
Clinical Implications
The findings highlight the importance of microbial interactions in determining S. aureus colonization and infection risk. By identifying individuals who are persistent carriers, clinicians can more effectively target preventive treatments such as nasal decolonization. Moreover, the study opens avenues for microbiome-based strategies to reduce reliance on antibiotics.
The researchers plan to investigate how factors such as human genetics, sex, medical conditions, and environmental exposures influence S. aureus carriage.
Expert Perspectives
Dr. Dinesh Aggarwal of Imperial College London said, “Persistent S. aureus carriage is a major infection risk in hospitals. By uncovering bacterial profiles that protect against colonization, we can explore new microbiome-based ways to prevent infections without depending heavily on antibiotics.”
Katie Bellis from the Wellcome Sanger Institute added, “This is the largest study of the nasal microbiome ever conducted. It shows that S. aureus is part of a community, and some bacterial neighbors can help keep it out. This offers exciting new directions for infection prevention.”
Senior author Dr. Ewan Harrison emphasized the broader significance: “Everyone’s nasal microbiome is unique. By analyzing thousands of samples, we finally understand how these natural bacterial communities influence our susceptibility to infection.”