molecular identification and resistance patterns of streptococcus minor in canine nasal infections: a case report

This study aims to isolate, molecularly identify, and evaluate the antibiotic susceptibility profile of streptococcus minor recovered from the nasal cavity of a dog, thereby contributing to the understanding of its clinical significance and resistance patterns in veterinary medicine. a nasal swab sample was obtained from a dog presented to the veterinary clinic at the faculty of veterinary medicine, university of tehran, tehran, iran. initial isolation was performed on standard culture media, where the colonies were identified as small, round, unpigmented, and transparent with narrow zones of alpha-hemolysis. pure cultures were obtained and subjected to gram staining and catalase testing, confirming the presence of gram-positive, catalase-negative cocci, suggestive of streptococcus species. molecular identification was achieved through 16s rrna gene sequencing, which conclusively identified the isolate as streptococcus minor (ncbi genbank accession number: or857488). the antibiotic susceptibility of the isolate was assessed using the disc diffusion method with a comprehensive panel of antibiotics, including ampicillin, streptomycin, vancomycin, erythromycin, florfenicol, cefotaxime, cefepime, trimethoprim, methicillin, tetracycline, sulfamethoxazole-trimethoprim, amoxicillin-clavulanic acid, and penicillin. the streptococcus minor isolates demonstrated susceptibility to penicillin, clindamycin, erythromycin, and trimethoprim-sulfamethoxazole. conversely, resistance was noted against tetracycline, streptomycin, and methicillin, consistent with previously documented resistance patterns in related streptococcal species. this study provides critical insights into the identification and antibiotic susceptibility of streptococcus minor, a pathogen of emerging relevance in veterinary medicine. the observed resistance to multiple antibiotics underscores the necessity for ongoing surveillance and judicious use of antimicrobials in clinical settings. these findings not only enhance our understanding of streptococcus minor but also highlight the importance of tailored antibiotic therapy based on precise microbial identification and resistance profiling.