Comparative RNA-seq-Based Transcriptome Analysis of the Virulence Characteristics of Methicillin-Resistant and -Susceptible Staphylococcus pseudintermedius Strains Isolated from Small Animals

Staphylococcus pseudintermedius is often associated with pyoderma, which can turn into a life-threatening disease. The dissemination of highly resistant isolates has occurred in the last 10 years and has challenged antimicrobial treatment of these infections considerably. We have compared the carriage of virulence genes and biofilm formation between methicillin-resistant and methicillin-susceptibleS. pseudintermedius (MRSP and MSSP, respectively) isolates and theirin vitro gene expression profiles by transcriptome sequencing (RNA-seq). Isolates were relatively unevenly distributed among the fouragr groups, andagr type III predominated in MRSP. Five virulence genes were detected in all isolates. Only thespsO gene was significantly associated with MSSP isolates (P = 0.04). All isolates produced biofilm in brain heart infusion broth (BHIB)–4% NaCl. MSSP isolates produced more biofilm on BHIB and BHIB–1% glucose media than MRSP isolates (P = 0.03 andP = 0.02, respectively). Virulence genes encoding surface proteins and toxins (spsA ,spsB ,spsD ,spsK ,spsL ,spsN ,nucC ,coa , andluk-I ) and also prophage genes (encoding phage capsid protein, phage infection protein, two phage portal proteins, and a phage-like protein) were highly expressed in the MRSP isolate (compared with the MSSP isolate), suggesting they may play a role in the rapid and widespread dissemination of MRSP. This study indicates that MRSP may upregulate surface proteins, which may increase the adherence of MRSP isolates (especially sequence type 71 [ST71]) to corneocytes. MSSP isolates may have an increased ability to form biofilm under acidic circumstances, through upregulation of the entirearc operon. Complete understanding ofS. pseudintermedius pathogenesis and host-pathogen signal interaction during infections is critical for the treatment and prevention ofS. pseudintermedius infections.