Investigating the antibiotic resistance pattern of Corynebacterium pseudotuberculosis strains isolated from livestock in Mashhad

Molla Ahmadian Kaseb, Amin; Farzin, Hamid Reza; Chaichi Nosrati, Arash; Jamshidian Mojaver, Majid; Modiri, Leila

doi:10.22092/ari.2026.372115.4041

Investigating the antibiotic resistance pattern of Corynebacterium pseudotuberculosis strains isolated from livestock in Mashhad

Articles in Press

Document Type : Original Articles

Authors

¹ Department of Microbiology, La.C., Islamic Azad University, Lahijan, Iran.

² Razi Vaccine and Serum Research Institute, Agriculture Research, Education and Extension Organization (AREEO), Mashhad, Iran.

³ Department of Microbiology, La.C., Islamic Azad University, Lahijan.

10.22092/ari.2026.372115.4041

Abstract

Corynebacterium pseudotuberculosis is the causative agent of caseous lymphadenitis, one of the common and chronic diseases in sheep and goats. The disease hampers growth, increases carcass condemnation, incurring substantial daily losses for small holder farms.
The present study aimed to examine antibiotic resistance patterns, and determine the inhibition coefficient of isolates against commonly used antibiotics in livestock.
In this study, 91 samples were collected from adult sheep that presented with lymph node swelling and purulent discharge. The material was inoculated into brain heart infusion (BHI) broth and incubated; cultures were then sub cultured onto blood agar plates for further growth. Isolates suspected to be Corynebacterium pseudotuberculosis were identified and subsequently subjected to antibiotic susceptibility testing, performed by the Kirby–Bauer disk diffusion method and by determining minimum inhibitory concentrations (MICs).
Antibiotic sensitivity testing showed that the isolates had the lowest resistance to ciprofloxacin and gentamicin antibiotics at 15.3% and 15.8% respectively, and the highest resistance to penicillin and vancomycin antibiotics at 84.42% and 78.39% respectively. Based on MIC results for antibiotics commonly used in livestock treatment, inhibitory effects were between 8 to 64 micrograms per ML. Corynebacterium pseudotuberculosis is identified as one of the causative agents of skin abscesses in sheep in the province.
Given the high economic losses caused by this disease, preventive measures such as developing effective vaccination programs and adopting alternative control strategies are necessary. Furthermore, more extensive epidemiological studies are needed to assess the prevalence of caseous lymphadenitis in small ruminants in Iran.

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