Document Type : Original Articles
Authors
1
Faculty of Veterinary Medicine, University of Semnan, Semnan, Iran
2
Department of Clinical sciences, Faculty of Veterinary Medicine, University of Semnan, Semnan, Iran
3
Department of Pathobiology, Faculty of Veterinary Medicine, University of Semnan, Semnan, Iran
4
Department of Health Food Education, Faculty of Veterinary Medicine, Semnan University, Semnan, Iran
Abstract
Background: Diarrhea in calves is a major cause of mortality, treatment costs, and reduced growth on livestock farms. Bacterial diarrhea caused by pathogenic strains of Escherichia coli, including enterotoxigenic E. coli (ETEC), enterohemorrhagic E. coli (EHEC), and enteropathogenic E. coli (EPEC), is particularly significant in neonatal calves. Origanum vulgare L., a plant belonging to the mint family, is widely used in herbal medicine. Research has demonstrated its potent antibacterial activity, making it a promising candidate for combating bacterial infections in livestock.
Objectives: This study aimed to characterize the molecular factors associated with Escherichia coli isolates from calf diarrhea and to evaluate the antimicrobial efficacy of Origanum vulgare essential oil against these isolates.
Methods: Fecal samples (n=30) were collected from calves with diarrhea across multiple commercial dairy farms in Semnan County. Samples were cultured on MacConkey agar, and one Escherichia coli isolate per sample was confirmed using standard biochemical assays. All isolates underwent multiplex PCR to detect the presence of stx1, stx2, eaeA, and hlyA genes. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Origanum vulgare essential oil were determined against the isolates.
Results: Multiplex PCR analysis revealed that 11 of the 30 Escherichia coli isolates (36.7%) possessed at least one of the four virulence genes examined. Among these 11 isolates, seven (63.6%) carried the stx1 gene, nine (81.8%) had the stx2 gene, four (36.4%) took the eaeA gene, and seven (63.6%) carried the ehlyA gene. The MIC of Origanum vulgare essential oil was 800 ppm for eight isolates and 400 ppm for the remaining isolates. The MBC ranged from 400 ppm to 1600 ppm across all isolates. Of the 30 Escherichia coli isolates examined, 11 (36.7%) harbored at least one of the four virulence genes. Given the promising in vitro antibacterial activity observed, Origanum vulgare L. essential oil warrants further investigation as a potential complementary agent for the control or prevention of colibacillosis.
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