Abstract:
BACKGROUND : Antimicrobial resistance in staphylococci, often associated with treatment failure, is increasingly
reported in veterinary medicine. The aim of this study was to investigate patterns and predictors of antimicrobial
resistance among Staphylococcus spp. isolates from canine samples submitted to the bacteriology laboratory at the
University of Pretoria academic veterinary hospital between 2007 and 2012. Retrospective data of 334
Staphylococcus isolates were used to calculate the proportion of samples resistant to 15 antimicrobial agents. The
Cochran-Armitage trend test was used to investigate temporal trends and logistic regression models were used to
investigate predictors of antimicrobial resistance in Staphylococcus aureus and Staphylococcus pseudintermedius.
RESULTS : Results show that 98.2% (55/56) of the S. aureus isolates were resistant to at least one drug while 42.9%
were multidrug resistant. Seventy-seven percent (214/278) of the S. pseudintermedius isolates were resistant to at
least one drug and 25.9% (72/278) were multidrug resistant. Resistance to lincospectin was more common among
S. aureus (64.3%) than S. pseudintermedius (38.9%). Similarly, resistance to clindamycin was higher in S. aureus (51.8%)
than S. pseudintermedius (31.7%) isolates. There was a significant (p = 0.005) increase in S. aureus resistance to
enrofloxacin over the study period. Similarly, S. pseudintermedius exhibited significant increasing temporal trend in
resistance to trimethoprim-sulphamethoxazole (p = 0.004), clindamycin (p = 0.022) and orbifloxacin (p = 0.042).
However, there was a significant decreasing temporal trend in the proportion of isolates resistant to doxycycline
(p = 0.041), tylosin (p = 0.008), kanamycin (p = 0.017) and amoxicillin/clavulanic acid (p = 0.032).
CONCLUSIONS : High levels of multidrug resistance and the increasing levels of resistance to sulphonamides,
lincosamides and fluoroquinolones among Staphylococcus spp. isolates in this study are concerning. Future studies
will need to investigate local drivers of antimicrobial resistance to better guide control efforts to address the
problem.
