Investigation of the antibiotic resistance and biofilm formation of Staphylococcus pseudintermedius strains isolated from canine pyoderma.

The aim of the present study was to investigate the antibiotic resistance and bio lm formation among a collection of 51 clinical isolates of Staphylococcus pseudintermedius collected from canine pyoderma. All isolates were tested for the susceptibility to a panel of 14 antimicrobial agents by the disk di usion method in Müeller-Hinton agar. Oxacillin resistance was detected by subculture on oxacillin screening agar base. Bio lm formation was investigated by the Microtitre Plate test (MtP) and for some strains by transmission electron microscopy (TEM). Antibiotic resistance pro ling demonstrated that 45/51 S. pseudintermedius isolates had a multi drug resistant (MDR) phenotype, exhibiting simultaneous resistance to at least 3 antibiotics categories; whereas 6 isolates showed a non-MDR phenotype. Thirty strains (59%) were resistant in oxacillin resistant screening agar, the same strains were also positive for mecA by PCR assay. All S. pseudintermedius isolates showed bio lm production by MtP method. Seventeen out of 51 isolates were classi ed as weakly adherent, 26 as moderately adherent, and 8 as strongly adherent. Moreover, no di erence in bio lm formation between meticillin-resistant S. pseudintermedius (MRSP) and meticillin-suscebtible S. pseudintermedius (MSSP) (P value > 0.05) was noted. The antimicrobial resistance mechanisms and bio lm formation could explain the di culty in treating S. pseudintermedius canine infections, chemotherapeutic failure, and consequently persistent infections.