Vetnews | Desember 2025 8 « BACK TO CONTENTS Analysis by antimicrobial class revealed that the most frequent resistance in both groups occurred within the tetracycline class. In isolates from dogs with otitis externa, 37.5% were resistant to tetracyclines, 23.1% to β-lactams, and 21.9% to lincosamides. In isolates from the ears of healthy dogs, the corresponding resistance rates were 25%, 19.7%, and 22.4%, respectively. All isolates were fully susceptible to glycopeptides, oxazolidinones, fusidanes, and glycylcyclines (Table 2). 2.4 Distribution of MDR and MRSP Strains. Regarding MDR, 14 strains (8.7%) were isolated from samples collected from dogs with otitis externa (Table 3), while 3 strains (4%) were isolated from samples taken from the ears of healthy dogs (Table 4). Additionally, two MRSP strains (1.2%) were isolated from samples collected from dogs with otitis externa (Table 3). Regarding the MRSP strains, in addition to resistance to β-lactam antibiotics, they also exhibited resistance to antimicrobials from the following classes: aminoglycosides, tetracyclines, fluoroquinolones, macrolides, lincosamides, and sulfonamides + pyrimidines (Table 3). A comparative statistical analysis of S. pseudintermedius prevalence and antimicrobial resistance between isolates from dogs with otitis externa and those from clinically healthy dogs is presented below (Table 5). This analysis includes p-values, false discovery rate (FDR)-adjusted q-values, risk differences (RD), and relative risks (RR) with 95% confidence intervals, providing an inferential assessment of the significance and magnitude of the observed differences. Antimicrobial Resistance Number of Strains and Percentage Susceptible to all tested antimicrobials 61 (38.1%) PEN 14 (8.8%) TET 37 (23.1%) CLI 25 (15.6%) TET + PEN 9 (5.6%) PEN + TET + CLI 8 (5%) PEN + TET + SXT 4 (2.5%) PEN + OXA + GEN + TET + CIP + MXF + ERY + CLI + SXT 2 (1.2%) Table 3: Antimicrobial resistance profiles of S. pseudintermedius strains isolated from dogs with otitis externa (distribution according to the resistance profile of each strain) Antimicrobial Resistance Number of Strains and Percentage Susceptible to all tested antimicrobials 31 (40.8%) CLI 14 (18.4%) TET 16 (21.1%) PEN 12 (15.8%) PEN + TET + CLI 3 (4%) Table 4. Antimicrobial resistance of S. pseudintermedius strains isolated from the ears of healthy dogs (distribution based on resistance profile of each isolate) Antimicrobial/ Parameter Otitis Externa (n/N, %) Healthy Dogs (n/N, %) p-Value q-Value (FDR) Risk Difference (%, 95% CI) Relative Risk (95% CI) Prevalence (S. pseudintermedius) 160/400 (40.0%) 76/360 (21.1%) <0.0001 — 18.9% (12.2%, 25.6%) 1.90 (1.52–2.36) Penicillin resistance 37/160 (23.1%) 15/76 (19.7%) 0.5712 0.6614 3.4% (−8.4%, 15.2%) 1.17 (0.67–2.04) Oxacillin resistance (MRSP) 2/160 (1.3%) 0/76 (0.0%) 0.5303 0.6614 1.3% (−1.3%, 4.0%) 3.39 (0.17–66.7) Gentamicin resistance 2/160 (1.3%) 0/76 (0.0%) 0.5303 0.6614 1.3% (−1.3%, 4.0%) 3.39 (0.17–66.7) Tetracycline resistance 60/160 (37.5%) 19/76 (25.0%) 0.0714 0.1429 12.5% (−1.1%, 26.1%) 1.50 (0.96–2.33) Ciprofloxacin resistance 2/160 (1.3%) 0/76 (0.0%) 0.5303 0.6614 1.3% (−1.3%, 4.0%) 3.39 (0.17–66.7) Moxifloxacin resistance 2/160 (1.3%) 0/76 (0.0%) 0.5303 0.6614 1.3% (−1.3%, 4.0%) 3.39 (0.17–66.7) Erythromycin resistance 2/160 (1.3%) 0/76 (0.0%) 0.5303 0.6614 1.3% (−1.3%, 4.0%) 3.39 (0.17–66.7) Clindamycin resistance 35/160 (21.9%) 17/76 (22.4%) 0.9284 0.9284 −0.5% (−12.8%, 11.8%) 0.98 (0.58–1.64) Trimethoprim– Sulfamethoxazole resistance 6/160 (3.8%) 0/76 (0.0%) 0.1832 0.3664 3.8% (−0.9%, 8.4%) 6.15 (0.35–107.8) MDR (≥3 classes) 14/160 (8.7%) 3/76 (4.0%) 0.2845 0.4735 4.7% (−3.9%, 13.3%) 2.17 (0.64–7.31) MRSP (oxacillin-resistant) 2/160 (1.3%) 0/76 (0.0%) 0.5303 0.6614 1.3% (–1.3%, 4.0%) 1.39 0.17–66.7) Legend: PEN—penicillin; OXA—oxacillin; GEN—gentamicin; TET—tetracycline; CIP—ciprofloxacin; MXF— moxifloxacin; ERY—erythromycin; CLI—clindamycin; SXT—trimethoprim + sulfamethoxazole. Legend: PEN—penicillin; CLI—clindamycin; TET—tetracycline. Table 5. Statistical comparison of antimicrobial resistance rates in S. pseudintermedius isolates from dogs with otitis externa and from clinically healthy dogs Leading Article Antimicrobial Resistance Profile of Staphylococcus pseudintermedius ..... <<< 7
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