Selection of Lactobacillus strains from native chicken feces for the fermentation of purple onion (Allium cepa L.) as an antibiotic alternative against Salmonella spp. in chickens.

Background: The increasing prevalence of antibiotic resistance in poultry pathogens necessitates the development of sustainable alternatives to antibiotics. Probiotics, particularly Lactobacillus spp., have shown promise in combating bacterial infections in poultry. Purple onion extract (OE) possesses antibacterial properties and can potentially enhance the probiotic efficacy of Lactobacillus strains.

Aim: This study aimed to develop a biological product based on Lactobacillus-fermented OE (LFOE) as a sustainable alternative to antibiotics for the control of Salmonella-induced diarrhea in poultry.

Methods: Lactobacillus strains were isolated from native free-range chicken feces and screened for their antibacterial activity against Salmonella pullorum NCTC10705 and Salmonella typhimurium FC13827, as well as their survival rate in OE. Six promising strains were selected and further characterized for their ability to ferment OE and their co-aggregation ability against the pathogenic bacteria using scanning electron microscopy (SEM). 16S rRNA gene sequencing was performed for bacterial identification. The selected strain was used for fermentation in OE, and the resulting product was freeze-dried into a biological preparation. In vivo studies in chicks were conducted to assess the safety and intestinal persistence of LFOE.

Results: From an initial pool of 68 Lactobacillus strains, six promising candidates (L. plantarum 1582, L. plantarum WCFS1, L. plantarum JDM1, L. acidophilus NCFM, L. agilis DSM 20509, and L. agilis La3) were selected based on their antibacterial activity and high survival rate in OE. SEM confirmed the ability of these strains to ferment OE and co-aggregate with pathogenic bacteria. 16S rRNA gene sequencing confirmed their taxonomic identity as Lactobacillus. L. plantarum 1582, selected for its superior probiotic properties, was used to ferment LFOE, which proved safe for chicks and demonstrated the strain's ability to survive temporarily in the intestine.

Conclusion: This study successfully developed a biopreparation based on LFOE as a potential alternative to antibiotics for the control of Salmonella-induced diarrhea in poultry. However, regular re-supplementation is required to maintain probiotic efficacy due to the transient nature of intestinal colonization.