Dietary supplementation with allicin enhances growth performance and antioxidant capacity, and reduces gut pathogens and antibiotic resistance genes in Trachidermus fasciatus.

Allicin, a bioactive sulfur compound from garlic known for its antimicrobial and immunomodulatory properties, was evaluated in this study for its effects on growth, antioxidant activity, gut microbiota, and antibiotic resistance genes (ARGs) in Trachidermus fasciatus. Fish were administered allicin at concentrations of 100 mg/kg, 200 mg/kg, and 300 mg/kg. The 200 mg/kg allicin group had significantly higher WGR, LGR, and SGR than the control group. Hepatic SOD and LZM activities were also higher in the 200 mg/kg group. Metagenomics showed that allicin altered the gut microbiota composition, decreased the diversity, and altered the community structure. Allicin-treated fish had significantly reduced levels of potentially damaging bacteria, including Pseudomonas and Vibrio species. The ARGs showed that genes associated with multidrug resistance, including specific subtypes, were markedly reduced in the 200 mg/kg allicin-treated fish. The control group had a markedly decreased number of genes resistant to β-lactam antibiotics. Allicin reduced the number of genes resistant to rpoB2 and mdtC, suggesting the potential for antibiotic resistance. Network analysis of co-occurrence patterns showed that genes resistant to multiple drugs, tetracyclines, and peptides were prevalent, with most possible potential host taxa belonging to Ascomycota and Firmicutes. These results indicate the importance of allicin for fish health as a sustainable alternative to antibiotic resistance and provide a viable alternative to antibiotic resistance for fish farming.