Virulence Potential, Antimicrobial Susceptibility and Phylogenetic Analysis of Corynebacterium pseudotuberculosis Isolated from Caseous Lymphadenitis in Sheep and Goats in Duhok City, Iraq

Abstract

Caseous lymphadenitis is a bacterial disease caused by Corynebacterium pseudotuberculosis affecting sheep and goats worldwide. It has been previously shown that the CLA is highly prevalent in sheep and goats in Duhok city. Therefore, this study is aimed to study virulence genes, the susceptibility pattern toward antimicrobial agents and to analyse the phylogenetic relationship of C. pseudotuberculosis based on the partial rpoB gene sequences. The results showed that the virulence genes including pld, fagA, B, C and D were identified 100% in all 22 isolates used in this study. Antibiotics sensitivity test showed varying degrees of susceptibility patterns against cefotaxime, clarithromycin, gentamicin, rifampin, amoxicillin and trimethoprim/sulphamethoxazole. The isolates were found to be sensitive 100% to chloramphenicol, doxycycline, norfloxacin, ciprofloxacin, clindamycin, erythromycin, ceftriaxone, levofloxacin. The overall degree of resistance was very low, with the exception of amoxicillin which was 81.8%. Nucleotide sequence analysis of the 22 rpoB sequences detected the overall similarity of 97, 98, 99 and 100% with biovar ovis of the reference sequences. Phylogenetic tree of partial sequences of the rpoB gene showed that the biovar ovis isolates from both sheep and goat are grouped together in the same lineage and the nucleotide variation between the sequences does not change the protein expression. In conclusion, for the first time in Duhok and in Iraq, phylogenetic tree clearly confirmed the C. pseudotuberculosis subspecies differentiation based on rpoB sequences from sheep and goats with CLA.