Antimicrobials from a feline skin commensal bacterium inhibit skin colonization and infection by drug-resistant S. pseudintermedius

Methicillin-resistant Staphylococcus pseudintermedius (MRSP) is an important emerging zoonotic pathogen that causes severe skin infections. To combat infections from drug-resistant bacteria, the transplantation of commensal antimicrobial bacteria as a therapeutic has shown clinical promise. We screened a collection of diverse staphylococcus species from domestic dogs and cats for antimicrobial activity against MRSP. A unique strain (S. felis C4) was isolated from feline skin that inhibited MRSP and multiple gram-positive pathogens. Competition experiments in mice showed that S. felis significantly reduced MRSP skin colonization and an antimicrobial extract from S. felis significantly reduced necrotic skin injury from MRSP infection. Fluorescence and electron microscopy revealed that S. felis antimicrobials disrupted bacterial but not eukaryotic cell membranes. LC/MS identified several S. felis phenol-soluble modulin beta (PSMβ) peptides that exhibited antimicrobial and anti-inflammatory activity. These findings indicate a feline commensal bacterium that could be utilized in bacteriotherapy against difficult-to-treat animal and human skin infections.

Methods
NHEK cells were treated with DMSO (0.1%) control, PSMβ2 (10 μg/ml), Poly I:C (0.4 μg/ml) or PSMβ2 and Poly I:C combined, all in triplicate wells, for 4 h or 24 h in and RNA was extracted using the PureLink RNA mini kit and triplicate samples were pooled together for each treatment. Isolated RNA was submitted to the UCSD IGM Genomics Center for RNA-sequencing performed on a high-output run V4 platform (Illumina, USA) with a single read 100 cycle runs. All the steps including trim bases, alignment with bowtie 2, quantification to annotation model (Partek E.M), Normalization (CPM/Add 1.0 E-4), Gene Set Enrichment (GSA), Differential Gene Analysis and hierarchial clustering, and Gene Ontology analysis was performed with the Partek Flow Genomics Suite.