Investigation of the Presence and Antimicrobial Susceptibilities of Corynebacterium pseudotuberculosis in Subclinical Mastitis in Cattle Raised in the Aegean Region

Abstract: This study aims to investigate the presence of Corynebacterium pseudotuberculosis and its antimicrobial susceptibility in cattle with subclinical mastitis in the Aegean Region. In 2024, 200 milk samples were collected from dairy farms in the region where subclinical mastitis was identified using the California Mastitis Test. The samples were analyzed through culture, Gram staining, and biochemical testing. Suspected isolates were confirmed using the VITEK 2 system and molecularly identified by PCR targeting the PIP gene. Antimicrobial susceptibility was assessed via the Kirby-Bauer Disk Diffusion Method. Seven Corynebacterium pseudotuberculosis isolates were identified in the analysis. Antimicrobial susceptibility tests showed 71% sensitivity to enrofloxacin and gentamicin, 57% to amoxicillin-clavulanic acid, and 43% to oxytetracycline. In conclusion, although the detection rate of Corynebacterium pseudotuberculosis was low, it remains a significant pathogen in cattle with subclinical mastitis. Further studies on antibiotic resistance are essential for developing effective treatment strategies.