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TCD researchers discover how MRSA bacterium is carried in human nose

Scientists say the discovery “opens new avenues” for reducing the number of MRSA infections.

RESEARCHERS AT TRINITY College Dublin say they have discovered the mechanism by which a bacterium which has the potential to cause severe invasive disease, including MRSA infections, colonises the human nose.

A collaboration between researchers at the School of Biochemistry and Immunology and the Department of Microbiology at Trinity College Dublin has identified a mechanism by which the bacterium Staphylococcus aureus (S. aureus) colonises human nasal passages. The research, published in the prestigious journal PLOS Pathogens, shows for the first time that a protein located on the bacterial surface called “clumping factor B” (ClfB) recognises a protein called “loricrin” that is a major component of the envelope of cells in the nose and skin.

‘S. aureus’ colonises 20 per cent of the population

S. aureus is a human pathogen and a major concern in hospitals and other healthcare facilities, where many infections are caused by strains like MRSA that are resistant to commonly used antibiotics.

The pathogen S. aureus persistently colonises about 20 per cent of the human population by binding to skin-like cells within the nasal cavity. The team explained that being ‘colonised’ predisposes an person towards becoming infected, underlining the importance of understanding the mechanisms involved.

ClfB was previously shown to promote S. aureus colonisation in a human nasal volunteer study, according to researchers. The results of the study revealed that ClfB binding to loricrin was crucial for successful colonisation of the nose in a mouse model.

Mouse study

In the study, a mouse lacking loricrin allowed fewer bacterial cells to colonise its nasal passages than a normal mouse; meanwhile, when S. aureus strains that lacked ClfB were used, nasal colonisation was dramatically reduced. Finally it was shown that soluble loricrin could reduce binding of S. aureus to human nasal skin cells and that nasal administration of loricrin reduced S. aureus colonisation of mice.

“Loricrin is a major determinant of S. aureus nasal colonisation. This discovery opens new avenues for developing therapeutic strategies to reduce the burden of nasal carriage and consequently infections with this bacterium. This is particularly important given the difficulties associated with treating MRSA infections,” Trinity’s Assistant Professor at the School of Biochemistry and Immunology Rachel McLoughlin  and Professor of Molecular Microbiology Tim Foster, the study’s corresponding authors, wrote.

Read: Rates of MRSA drop to the lowest recorded in Ireland

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