Nasal microbiome inhabitants with anti- <i>Staphylococcus aureus</i> activity

<i>Staphylococcus aureus</i> (SA) is a common member of the human microbiota, colonizing people transiently throughout life, and SA nasal carriage is an important reservoir for the spread of this bacterium. The global economic toll of SA infections is enormous, and antibiotic-resistant strains continue to emerge. Therefore, new approaches to decolonize carriers of SA are urgently needed. To better understand the dynamics of nasal SA carriage versus non-carriage, we monitored subjects longitudinally and isolated and identified species that associate with SA culture-negative noses. While several members of the <i>Gammaproteobacteria</i> class demonstrated anti-SA activity, the nasal <i>Klebsiella</i> spp. potently inhibited (>99%) SA survival in a contact-independent manner. For multiple nasal isolates of <i>K. aerogenes</i> from our donor cohort, this inhibition was attributed to a small, cationic, proteinaceous molecule(s). The secreted products of nasal <i>Gammaproteobacteria</i> (e.g., <i>Klebsiella</i>/<i>Serratia</i> spp.) warrant further investigation as potential sources of new SA decolonization agents.