Antibiotic Resistance Profiles and pld Gene Distribution in Corynebacterium pseudotuberculosis Isolates from Small Ruminants in Razavi Khorasan Province, Iran

Molla Ahmadian Kaseb, Amin; Farzin, Hamidreza; Chaichi Nosrati, Arash; Jamshidian-Mojaver, Majid; Modiri, Leila

doi:10.22092/ari.2026.366912.3774

Antibiotic Resistance Profiles and pld Gene Distribution in Corynebacterium pseudotuberculosis Isolates from Small Ruminants in Razavi Khorasan Province, Iran

Articles in Press

Document Type : Original Articles

Authors

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

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

10.22092/ari.2026.366912.3774

Abstract

Introduction: Caseous Lymphadenitis (CLA), caused by Corynebacterium pseudotuberculosis, is a serious infectious disease in small ruminants with limited treatment options and significant economic implications for livestock production.
Objective: This study investigated antibiotic resistance patterns and toxin production in resistant isolates of C. pseudotuberculosis based on the Pld gene in Razavi Khorasan Province.
Materials and Methods: C. pseudotuberculosis samples were systematically collected from 350 central slaughterhouses in Razavi Khorasan Province from small ruminant carcasses displaying characteristic lesions. Antimicrobial sensitivity testing, Minimum Inhibitory Concentration (MIC), and Minimum Bactericidal Concentration (MBC) for commonly used antibiotics were determined using standardized protocols. ERIC-PCR was employed to identify the type of Pld gene among the isolated strains and compare the results with antibiotic sensitivity profiles to establish genotype-phenotype correlations.
Results: Out of the samples tested, 40 were confirmed to be infected with the target bacteria through cultivation on specific selective media and routine biochemical tests including catalase and urease assays. The isolated corynebacteria displayed varying degrees of resistance and sensitivity to the tested antibiotics with distinct patterns. Notably, the highest resistance rates were observed against vancomycin (75%), tetracycline (72.5%), and cefotaxime (60%). Among the isolates, 45.8% were classified as multi-drug resistant (MDR), representing a concerning public health issue. ERIC-PCR dendrogram analysis revealed significant genetic similarities between isolates from sheep and goats, suggesting potential cross-species transmission pathways.
Conclusion: This comprehensive study enhances the epidemiological understanding of C. pseudotuberculosis and highlights the importance of ERIC-PCR as a reliable molecular method for genotyping and characterizing this pathogen, which can inform evidence-based selection of appropriate antibiotic treatments.

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