Sessions

Antimicrobial resistance (AMR) represents a significant animal and public health concern, complicating the treatment of bacterial infections in companion animals. Staphylococcus pseudintermedius is an important pathogen associated with canine skin and soft tissue infections, with methicillin resistance posing a major therapeutic challenge. Enrofloxacin is an antibiotic classified in the AMEG-B category and considered critically important, making its prudent use of particular importance. Pharmacokinetic/pharmacodynamic (PK/PD) analysis plays a key role in promoting the prudent use of this antibiotic.

The aim of this study was to characterize the pharmacokinetics of enrofloxacin in canine blood plasma and interstitial fluid (ISF), and to compare the resulting exposure with susceptibility data from S. pseudintermedius isolates. The animals received a single oral (per os) dose of enrofloxacin at approximately 20 mg/kg. Pharmacokinetic analysis was performed using a non-compartmental analysis (NCA) approach. The antimicrobial susceptibility of S. pseudintermedius isolates to enrofloxacin was determined using the broth microdilution method.

The Cmax of enrofloxacin was 2.94 ± 1.39 µg/ml in blood plasma and 3.77 ± 2.07 µg/ml in ISF, while the AUC₀-₂₄ was 21.64 ± 15.43 µg×h/ml in plasma and 44.93 ± 29.15 µg×h/ml in ISF. In the pharmacodynamic analysis, 243 canine S. pseudintermedius isolates were evaluated, of which 196 (80.7%) were classified as methicillin-susceptible (MSSP) and 47 (19.3%) as methicillin-resistant (MRSP) isolates. Of the MSSP isolates, 61.7% were susceptible to enrofloxacin, whereas only 6.4% of the MRSP isolates were susceptible.

In the PK/PD analysis, the AUC₀-₂₄/MIC₉₀ ratio was 2.71 h in blood plasma and 5.62 h in ISF. The Cmax/MIC₉₀ ratio was 0.37 in blood plasma and 0.47 in ISF. These findings highlight that the clinical use of enrofloxacin for the treatment of skin infections caused by S. pseudintermedius should be recommended only following appropriate antimicrobial susceptibility testing and PK/PD analysis. Failure to implement such an approach may contribute to a further increase in the prevalence of resistant strains, thereby posing risks to both animal and public health.