Fermented purple onion () and chive () bulb extracts as antibiotic alternatives against toxin-carrying bacteria: In vitro and pathogenicity assessment in chickens.

Abstract

BACKGROUND: Antibiotic resistance inandspp. poses a significant threat to poultry health and productivity. Overuse of antibiotics in poultry farming has led to the emergence of multidrug-resistant (MDR) pathogens, which have contributed to food safety concerns and limited treatment options. Natural antimicrobial alternatives, particularly herbal agricultural products such as purple onions and chives, have gained interest as sustainable solutions. Furthermore, fermentation with probiotic bacteria enhances the antimicrobial properties of botanical extracts, improving their efficacy against pathogenic bacteria. AIM: This study aimed to evaluate the antibacterial efficacy of fermented purple onion (FPO) and fermented chive (FC) extracts againstandspp., both causative agents of diarrhea, in broiler chickens. The research also compared their effectiveness with conventional antibiotics used in poultry farming. METHODS: We fermented fresh purple onion and chive extracts usingandfor 72 hours under anaerobic conditions. Pathogenic(22) andspp. (9) were isolated from 30 diarrheal chicken fecal samples and identified through biochemical tests,virulence testing in chicks, polymerase chain reaction detection of toxin genes (, and), and 16S rRNA sequencing. The antibacterial activity of the fermented extracts was evaluated using disk diffusion assays, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) tests. The bioactive compound content, including phenolics, flavonoids, and sulfur compounds, was quantified using an aluminum chloride colorimetric assay to assess their contribution to antimicrobial efficacy. RESULTS: virulence assessment of chickens revealed that 4strains (18.2%) and 5strains (26.3%) induced diarrhea. Of these, 2strains (50%) harbored thetoxin gene, and all 5strains (100%) carried thegene. 16S rRNA gene sequencing identified 2strains and 4strains. All bacterial isolates exhibited MDR, particularly beta-lactam and macrolide antibiotics. Both fermented extracts exhibited significant antibacterial activity against MDRandspp., with FC exhibiting superior efficacy compared to FPO. The inhibition zones of FC (12.5-17.6 mm) were significantly larger than those of FPO (10.1-16.8 mm), particularly againstFG31-1 andNCTC10705. The MIC and MBC values indicated that FC had a stronger bactericidal effect, requiring lower concentrations to inhibit and kill bacterial growth. FC contained higher levels of flavonoids and allicin, which were correlated with its enhanced antibacterial properties. CONCLUSION: FPO and FC, particularly FPO, show strong antibacterial potential as natural alternatives to antibiotics in poultry farming. Their ability to inhibit MDR pathogens suggests their role in reducing antibiotic dependency and improving poultry health. Further,studies and commercial formulation strategies are required to validate the practical application of these formulations in the poultry industry.