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Sci Rep. 2016 Jun 16;6:27870. doi: 10.1038/srep27870.

Nasal commensal Staphylococcus epidermidis counteracts influenza virus.

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Department of Veterinary Medicine, National Taiwan University, Taipei, Taiwan.
Department of Dermatology, University of California, San Diego, CA, USA.
Division of Infectious Diseases, Department of Medicine, University of California, San Diego, CA, USA.
Moores Cancer Center, University of California, San Diego, CA, USA.
Institut für Medizinische Mikrobiologie, Virologie und Hygiene, Universitätsklinikum, Hamburg, Germany.


Several microbes, including Staphylococcus epidermidis (S. epidermidis), a Gram-positive bacterium, live inside the human nasal cavity as commensals. The role of these nasal commensals in host innate immunity is largely unknown, although bacterial interference in the nasal microbiome may promote ecological competition between commensal bacteria and pathogenic species. We demonstrate here that S. epidermidis culture supernatants significantly suppressed the infectivity of various influenza viruses. Using high-performance liquid chromatography together with mass spectrometry, we identified a giant extracellular matrix-binding protein (Embp) as the major component involved in the anti-influenza effect of S. epidermidis. This anti-influenza activity was abrogated when Embp was mutated, confirming that Embp is essential for S. epidermidis activity against viral infection. We also showed that both S. epidermidis bacterial particles and Embp can directly bind to influenza virus. Furthermore, the injection of a recombinant Embp fragment containing a fibronectin-binding domain into embryonated eggs increased the survival rate of virus-infected chicken embryos. For an in vivo challenge study, prior Embp intranasal inoculation in chickens suppressed the viral titres and induced the expression of antiviral cytokines in the nasal tissues. These results suggest that S. epidermidis in the nasal cavity may serve as a defence mechanism against influenza virus infection.

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