Emerging threat to antibiotic resistance: Impact of mycotoxin deoxynivalenol on gut microbiota and clonal expansion of extensively drug-resistant enterococci

Mycotoxins, antibiotic-resistant bacteria (ARB), and antibiotic resistance genes (ARGs) are significant environmental pollutants that pose considerable threats to environmental health and human safety through the food chain. This study is the first to investigate the impact of deoxynivalenol (DON), the most common mycotoxin, on antibiotic resistance dynamics in gut microbiota, demonstrating that DON exposure significantly selects for ARB and ARGs. Results indicated that 80.69 % of the ARGs with the highest increase in the DON group were exclusive to gram-positive bacteria, particularly those related to daptomycin. DON exposure enhanced the expression of virulence factors in gram-positive bacteria and increased reactive oxygen species (ROS) production and membrane permeability, compromising bacterial integrity and amplifying resistance mechanisms. DON also boosted the diversity and co-occurrence of ARGs and mobile genetic elements (MGEs), potentially facilitating the horizontal transfer of resistance traits. Notably, the dominant bacterial species isolated from broiler gut microbiota was identified as Enterococcus faecalis, which exhibited clonal expansion of sequence type ST123. This ST123 clone accounted for 86 % of the DON group and was associated with an extensively drug-resistant (XDR) phenotype, showing resistance levels exceeding 128 μg/mL to last-resort antibiotics such as daptomycin, vancomycin, and linezolid. Additionally, DON upregulated the expression of critical daptomycin resistance genes (liaR, walK, liaS, mprF, and cls) in vancomycin-resistant enterococci (VRE) isolates. This study highlights the microbiological and environmental hazards that mycotoxins pose to the antibiotic resistance crisis.