Species identification

Collected swabs were placed in 2 ml of liquid brain–heart infusion broth (BHI) (Oxoid, Basingstoke, United Kingdom), and were incubated at 37 °C for 24 h. The material was then subcultured onto solid media, and incubated for another 24 h. Presumptive identification of Staphylococcus was based on colony morphology on blood agar and mannitol salt agar plates (Oxoid, Basingstoke, United Kingdom), Gram staining, and the detection of enzyme production (coagulase tube test; IBSS Biomed, Poland). A single colony from selected coagulase-positive pure strains was further identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), as previously described¹⁶. Raw spectra were processed using MALDI Biotyper v.3.1 software (Bruker Daltonik GmbH, Germany). The results were classified using the score values proposed by the manufacturer. The final conformation of each S. pseudintermedius isolate was conducted using polymerase chain reaction restriction fragment length polymorphism PCR-RLFP analysis with the primers for the pta gene and reaction conditions previously described by Malisova et al.¹⁷.