Abstract
Sheep caseous lymphadenitis (CLA) causes significant economic losses in the livestock sector by causing a loss in the quantity and quality of animal products and a loss in the breeding value of animals. Although the primary agent in CLA's etiology is Corynebacterium pseudotuberculosis, some other opportunistic microorganisms also play a role. Therefore, the control and treatment of CLA necessitates the identification of the relevant etiological agents. This study aimed to conduct an in vitro culture and molecular characterization (PCR analysis and 16S rRNA sequencing) of the bacteria involved in sheep CLA cases reported in the Çankırı province of Türkiye and determine the antibiotic susceptibility of the case isolates. In total, 82 (16.4%) of 500 sheep in five farms were diagnosed with CLA. Following the culture of the superficial abscesses samples, C. pseudotuberculosis was identified in 30 (36.59%) as a result of PCR, Pseudomonas spp. in 8 (9.76%), and Enterobacter cancerogenus in 1 (1.22%), as a result of 16S rRNA sequencing. These data revealed extensive heterogeneity among the Pseudomonas isolates, with hints of derivation from a common ancestry for some and phylogenetic similarity to isolates from Germany, Malaysia, and India. In contrast to the high susceptibility to cefoperazone and lincomycin, the high resistances of C. pseudotuberculosis and Pseudomonas spp. isolates to cephalothin, ceftiofur, cloxacillin, amoxicillin, and bacitracin were remarkable. Based on these findings, it was concluded that for an effective treatment and control of ovine CLA cases, there is a need to consider the possible involvement of opportunistic bacteria other than the primary causative agent, C. pseudotuberculosis. It also contributed to increasing the country-specific sequence data and establishing new taxa from a universal perspective.