Prevalence and Characterization of In Vitro Susceptibility Profile of Bacteria Harvested from Otitis Externa in Dogs

Abstract

Canine otitis externa is a complex disease with multiple causative factors, prominently involving bacteria. Antibiotics serve as the primary therapeutic approach for prevailing bacterial influence. However, indiscriminate antibiotic use results in the emergence of resistant strains. The escalating global threat of antimicrobial resistance (AMR) underscores the critical need for comprehensive investigations. The study involved 118 dogs with otitis externa from an animal hospital in Karachi, encompassing diverse breeds, ages, and genders. Ear swabs underwent bacterial culture, followed by incubation, colony examination, Gram staining, and biochemical tests for identification. Antibiotic susceptibility was assessed using the disc diffusion method following CLSI guidelines. Out of 118 dogs, 91(77.11%) exhibiting clinical symptoms were included, with 29.66% recorded positive in crossbreed, with 42.37% being females, according to age, the prevalence was higher in above four-year-old dogs (47.45%). Notably, Pseudomonas spp. (22.03%), followed by Staphylococcus spp. (17.79%), Escherichia coli (13.55%), Proteus spp. (9.32%), Streptococcus spp. (8.47%). Concerning the seasons, most cases of infection were recorded in spring (38 cases). The assessment of antibiotic sensitivity through the disc diffusion method revealed Enrofloxacin, Norfloxacin and Ciprofloxacin as generally effective. In contrast, notable resistance was observed for Amoxicillin, Gentamycin, Ampicillin and Penicillin, especially among both Gram-positive (G+) and Gram-negative (G-) bacteria. Comprehensive investigations into canine otitis externa are imperative due to the rising threat of antimicrobial resistance. The study highlights prevalent bacterial strains, seasonal trends, and antibiotic susceptibility patterns, emphasizing the need for judicious antibiotic use to mitigate resistance emergence.