Researchers Discover how Staphylococcus Aureus, Colonizing the Human Nose, Spreads MRSA

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Nose and Nasal Cavities

S. aureus colonizes the nose and nasal cavities. Image by National Cancer Institute

Could new research could reduce MRSA infections in hospital patients?

Researchers from the Department of Biochemistry and Immunology and Department of Molecular Microbiology at Trinity College Dublin in Ireland have identified how the bacterium Staphylococcus aureus colonizes human nasal passages. S. aureus is the precursor form to the antibiotic resistant bacterium MRSA, and the presence of the bacteria in the nose makes it a risk factor for infection.

How S. aureus Colonizes the Human Nose

S. aureus has the potential to cause severe invasive disease and is a major concern in hospitals and healthcare facilities, where infections are sometimes caused by antibiotic resistant strains such as MRSA (methicillin-resistant S. aureus). S. aureus colonizes at least 20% of the human population by binding to cells within the nasal cavity, which may cause an infection. A recent study, published in the  journal PLoS Pathogens, shows that a protein located on the bacterial surface, called clumping factor B (ClfB), recognizes a protein called loricrin – a major component of the cells inside the nose.

Bacterial Clumping Factor Binding to Loricrin Facilitates S. aureus Colonization

Previous studies have shown that ClfB encourages S. aureus colonization of the nasal cavities. This most recent study, however, actually identifies the mechanism by which ClfB encourages S. aureus nasal colonization.

The study found that ClfB binding to a protein called loricrin was crucial for successful colonization of the nose in mice, and that fewer bacterial cells colonized the nasal passages of a mouse lacking loricrin, compared to a normal mouse. When S. aureus strains lacking ClfB were used, nasal colonization was dramatically reduced, and nasal administration of loricrin reduced S. aureus colonization of the mice.

The results suggest that there is a way to reduce colonization, and disease risk in the process, but only if these results can be translated to humans.

Dock, Lock and Latch, and Mupirocin

The binding of ClfB to loricrin was also found to be crucial for S. aureus colonization in the human nose; soluble loricrin reduced the binding of S. aureus to human nasal skin cells. The researchers also found that the dock, lock and latch mechanism, a specific interaction between the proteins caused by a change in their structures as they interact, results in firm binding of S. aureus to the cells of the human nose.

We currently use the antibiotic mupirocin to reduce bacterial colonization in the nasal cavities, but need to review its use due to problems with antibiotic resistance. Understanding the molecular interactions and mechanisms of nasal colonization, such as dock, lock and latch, can help find new treatments.

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