People who carry persistently Staphylococcus aureus (S. aureus) in their noses have fewer types of other bacteria, and some bacteria may help prevent it S. aureus colonization.
These are the findings of the largest-ever study of the nasal microbiome, published today (December 2) in Nature communications.
In the study, researchers at the Wellcome Sanger Institute, the University of Cambridge, the University of Birmingham and Imperial College London analyzed nasal swabs from more than 1,000 healthy blood donors to explore the complex bacterial communities that live in the human nose.
The research sheds new light on how interactions between different bacterial species are key to understanding why some people are persistently colonized by S. aureus and also provides clinical insight to predict who may be most at risk S. aureus contamination.
S. aureus is a common bacteria that lives without symptoms in the nose of about 30 percent of people. It normally does not cause harm, but if it enters the body through wounds, cuts or surgical incisions it can cause serious infections. Infections from S. aureus it is the second most common cause of death associated with bacterial infections, after tuberculosis, causing approximately one million deaths annually. Certain strains, such as those resistant to methicillin S. aureus (MRSA), are resistant to common antibiotics, making infections more difficult to treat.
Historically, its carriers S. aureus have been classified into three groups: persistent carriers, intermittent carriers, and noncarriers. Persistent carriers are always positive for transfer S. aureus. An intermittent carrier is sometimes positive and non-carriers never show positive for carriage S. aureus.
Because S. aureus Carrying increases the risk of postoperative infections, hospitals often screen patients before procedures such as joint replacements, and may provide nasal treatments to reduce colonization. However, the nasal microbiome, unlike the gut microbiome, has not been studied in large populations, leaving much unknown about how S. aureus interacts with other nasal bacteria.
In a new study, researchers at the Sanger Institute and their colleagues tried to analyze a much larger group of people than in previous studies to fully understand how different bacteria can affect S. aureus colonization.
The study recruited volunteers from across England who had previously taken part in blood donation trials led by the University of Cambridge. The team collected three weekly nasal swabs from 1,100 healthy adults. Each sample was tested for S. aureus using standard laboratory culture techniques and DNA sequencing was performed to identify the full spectrum of bacterial species present in each nasal swab. The researchers used advanced statistical methods to uncover patterns in the nasal microbiome and determine whether S. aureus Transport could be predicted by the bacterial community.
The researchers found two key patterns in the microbiome. First, the team found that persistent carriers have a distinct microbiome with an abundance S. aureus and lack of other species in nasal samples.
Secondly, some bacteria such as e.g Staphylococcus epidermidis, Dolosigranulum pigrum, and Moraxella catarrhalis found to be less common in persistent carriers. The researchers suggest that these other species may help block it S. aureus colonization in noncarriers.
Using machine learning, the researchers were also able to predict who it persistently colonizes with S. aureus particularly well, offering a potential method for predicting infection risk.
Interestingly, the researchers also suggest that intermittent carriers are simply misclassified as persistent or non-carriers — the concept of intermittent carriage does not represent a true biological condition. They are likely to be non-carriers that have been exposed and received S. aureus for a short period of time.
This study highlights that interactions between different bacterial species are key to understanding why some people are persistently colonized by S. aureusputting them at greater risk of infection. The findings have important clinical implications. Identification of its carriers S. aureus could help predict the risk of infection and allow healthcare professionals to better target those who may benefit from preventive colonization treatments.
Researchers now want to build on that piece of the puzzle by looking at whether certain risk factors, such as medical conditions, gender, human genetics or other environmental exposures influence S. aureus transport.
“Persistent carriage of Staphylococcus aureus is a well-recognized risk factor for infection, particularly in hospital settings. By identifying bacterial profiles that protect against S. aureus colonization, our findings could inform new microbiome-based strategies to reduce infection risk without relying on antibiotics.“
–Dr. Dinesh Aggarwal, first author and Clinical Lecturer at Imperial College London
“This is the largest study to date of the bacteria that live in our noses and shows that Staphylococcus aureus doesn’t act alone – it’s part of a whole community. We found that certain bacterial neighbors can help keep staph out, offering exciting new directions for preventing infections using new methods.”
–Katie Bellis, co-author and scientist at the Wellcome Sanger Institute
“Everyone’s nose microbiome is unique, and this study shows that the bacteria that live there can have a big impact on our health. By studying thousands of samples, we can finally see the bigger picture of how our natural bacteria either help or prevent infection.”
-Dr. Ewan Harrison, senior author and team leader at the Wellcome Sanger Institute and the University of Cambridge
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