Multi-drug and methicillin resistance of staphylococci from canine patients at a veterinary teaching hospital (2006-2011).

BACKGROUND: Over the past 10 years, an increase in methicillin and multi-drug resistant staphylococcal species has been identified worldwide and anecdotally reported within our veterinary teaching hospital.
OBJECTIVE: To determine the methicillin resistance (MR) and multi-drug resistance (MDR) patterns of staphylococcal species isolated from canine patients between 2006 and 2011. ANIMALS AND METHODS: Staphylococcal isolates (n = 1069) were cultured from the canine patient population of the veterinary teaching hospital. The susceptibility reports of Staphylococcus pseudintermedius, S. aureus, S. schleiferi v. coagulans, S. schleiferi v. schleiferi, and other coagulase-negative staphylococci (CoNS) were assessed. Isolates were organized into five site categories. Isolates were scored on a 0-10 scale based on resistance to antimicrobial classes, with MDR classified as an isolate scoring a value ≥3. Statistical analysis included χ(2), Fisher's exact test, and ANOVA with mean square and post hoc analysis; p < 0.05 was significant.
RESULTS: S. pseudintermedius (76.6%), S. aureus (15.5%), S. schleiferi v. coagulans (5.7%), S. schleiferi v. schleiferi (1.2%), and CoNS (0.9%) isolation was observed. MR occurred in 11.4% of all combined isolates, with no difference between sites and years. Of the S. pseudintermedius isolates, 4.5% were methicillin resistant. Of all the isolates, 27.5% were MDR. The mean resistance score of S. pseudintermedius isolates increased significantly comparing 2006 and 2008 (p = 0.0006) and 2006 and 2009 (p = 0.0009). The mean score of all combined isolates increased significantly comparing 2006 and 2008 (p = 0.001).
CONCLUSION: MR staphylococci isolation is similar when compared to other studies. However, increased MDR isolation is of greater concern and high-scoring MDR staphylococci will limit our future antimicrobial choices.