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

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.

10.32598/ARI.81.3.3774

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. This study investigated antibiotic resistance patterns and toxin production in resistant isolates of C. pseudotuberculosis based on the pld gene in Khorasan Razavi Province.
Materials & Methods: C. pseudotuberculosis samples were systematically collected from 350 animals at central slaughterhouses in Khorasan Razavi 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. Enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) was employed to identify the presence of pld gene among the isolated strains and to compare the results with antibiotic sensitivity profiles in order 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 multidrug-resistant (MDR), representing a concerning veterinary and public health issue. ERIC-PCR dendrogram analysis revealed significant genetic similarities between isolates from sheep and goats, suggesting potential cross-species transmission.
Conclusion: This 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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Archives of Razi Institute
Volume 81, Issue 3
May and June 2026
Pages 681-692

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