Retrospective study on antimicrobial resistance in bacteria isolated from clinical infections in Dogs at a Brazilian Veterinary Teaching hospital

Antimicrobial resistance is an increasing concern impacting both human and animal health. This cross-sectional and retrospective study analyzed 1,108 clinical samples from dogs treated at a veterinary teaching hospital in Espírito Santo, Brazil, between 2019 and 2023. Microbiological cultures were performed on the samples, and antimicrobial susceptibility profiles were determined using the disk diffusion method. The objective was to identify the main pathogens, assess bacterial resistance patterns, and detect the presence of multidrug-resistant (MDR) bacteria. Of the samples analyzed, 793 (71.57%) showed bacterial growth, yielding a total of 1,140 isolates, as 268 samples were polymicrobial infections (involving more than one bacterial species). The most affected systems were the oto-dermal system (68.60% [782/1,140]), followed by the urinary system (23.25% [265/1,140]). Among the isolates, Gram-positive bacteria predominated (54.60% [623/1,140]), with Staphylococcus spp. being the most frequent (41.05% [468/1,140]). Among Gram-negative bacteria, the most prevalent species were Pseudomonas aeruginosa (11.75% [134/1,140]) and Escherichia coli (11.49% [131/1,140]). The highest resistance were associated with sulfonamides/trimethoprim, azithromycin, and ampicillin. Multidrug resistance was identified in 15.01% (136/906) of the isolates, mainly among Enterobacteriaceae (12.80% [116/906]). The findings suggest that bacterial resistance is associated with the intensive use of antimicrobials commonly prescribed by the clinical community in the study area and varies depending on the microorganism and the infected system. In conclusion, continuous surveillance is essential to guide the rational use of antimicrobials, thereby reducing the impact of bacterial resistance. Additionally, analyzing the resistance profiles of clinical isolates is crucial for the effective treatment of dogs requiring antibiotic therapy.