Investigation of Antibiotic Susceptibility Patterns in Bacteria Isolated During a Male Sheep Castration Surgery

There are different antibiotic resistance profiles among Yersinia spp. This pathogenic bacterial species causes yersiniosis worldwide, requiring testing of the organism's susceptibility in the local environment. An antibiotic susceptibility profile of a Yersinia spp. isolated from a castration surgical site was analyzed to provide insight into selecting appropriate antibiotics to treat Yersinia spp. infections while addressing antibiotic resistance issues effectively. The surgical site was swabbed before castration, and cultures were performed. Samples from the surgical site were taken after the procedure, cultured, and then incubated. CLSI 2020 guidelines were followed for interpreting antibiotic susceptibility tests. The Kirby-Bauer disk diffusion method was applied to better understand antibiotic susceptibility and resistance patterns, and a zone of inhibition measurement was used to determine the antibiotic effectiveness. Staining and microscopic examination of swab samples after surgery revealed a single colony of Gram-negative bacteria. Laboratory tests confirmed that the isolated Gram-negative bacilli were indeed Yersinia spp. Methyl Red and Voges-Proskauer tests showed negative results, while Citrate utilization testing demonstrated a positive result. A positive result was obtained for Yersinia spp. in the glucose fermentation test. Specifically, nitrofurantoin showed a significant zone of inhibition of over 17 mm, and gentamicin showed a zone of inhibition greater than 27 mm. However, resistance to ampicillin (11 mm), ceftriaxone, and cefazolin was observed. Due to the observed resistance to antibiotics, our results indicate that nitrofurantoin and gentamicin are likely to be the best options for treating Yersinia spp., in contrast to ampicillin, cefazolin, and ceftriaxone, which may be unsuitable due to resistance.