An exploration of mechanisms underlying Desemzia incerta colonization resistance to methicillin-resistant Staphylococcus aureus on the skin

Colonization of human skin and nares by methicillin-resistant Staphylococcus aureus (MRSA) leads to community spread of MRSA. This spread is exacerbated by transfer of MRSA between humans and livestock, particularly swine. Here we capitalized on the shared features between human and porcine skin, including shared MRSA colonization, to study novel bacterial mediators of MRSA colonization resistance. We focused on the poorly studied bacterial species Desemzia incerta, which we found to exert antimicrobial activity through a secreted product and exhibited colonization resistance against MRSA in an in vivo murine skin model. Using parallel genomic and biochemical investigation, we discovered that D. incerta secretes an antimicrobial protein. Sequential protein purification and proteomics analysis identified 24 candidate inhibitory proteins, including a promising peptidoglycan hydrolase candidate. Aided by transcriptional analysis of D. incerta and MRSA cocultures, we found that exposure to D. incerta leads to decreased MRSA biofilm production. These results emphasize the value in exploring microbial communities across a spectrum of hosts, which can lead to novel therapeutic agents as well as increased understanding of microbial competition.