Comparative Susceptibility of Pathogenic Methicillin-Resistant and Methicillin-Susceptible <em>Staphylococcus pseudintermedius</em> to Empirical Co-Trimoxazole for Canine Pyoderma

Abstract

The prevalence of methicillin-resistant Staphylococcus pseudintermedius (MRSP) that causes pyoderma has been gradually shifting, according to many surveillance studies, with annual changes. The empirical co-trimoxazole regimen remains interesting, but research on co-trimoxazole susceptibility to MRSP is limited. The objective of this study was to evaluate the susceptibility of co-trimoxazole to canine pyoderma MRSP isolates. Sixty isolates of S. pseudintermedius were identified as 16 MRSP and 44 methicillin-susceptible S. pseudintermedius (MSSP) using an oxacillin disk diffusion test and VITEK 2 system with VITEK GP card. Using the VITEK 2 system with a VITEK AST-GP81 card, the susceptibility rates of MRSP (15.00%) and MSSP (35.00%) to co-trimoxazole was observed. The median MIC of co-trimoxazole on MSSP (median, ≤10; IQR, 10–320) was lower than that of MRSP (median, ≥320; IQR, 10–320) (p = 0.5889, Mann-Whitney test). Percent attainment of PK/PD targets in MRSP (q 12 h, 43.75; q 8 h, 43.75) were lower than that of MSSP (q 12 h, 52.27; q 8 h, 52.27) (p = 0.7710). These findings show the moderately phenotypic co-trimoxazole susceptibilities of both MRSP and MSSP. Further study is required to develop clinical trials examining the use of co-trimoxazole in dogs with pyoderma.

Keywords

• antimicrobial resistance
• methicillin
• pharmacodynamics
• pyoderma
• staphylococci
• sulfamethoxazole