Mycotoxin deoxynivalenol drives antibiotic resistance evolution in Bacillus cereus via cell wall remodeling, compromising clinically critical antibiotics.

The molecular mechanism by which deoxynivalenol (DON) induces bacterial antibiotic resistance remains unexplored. As the most prevalent mycotoxin contaminant, DON poses significant public health risks due to the absence of dedicated monitoring standards in probiotic products. This study uncovers the previously unknown mechanism through which DON exposure drives antibiotic resistance evolution via bacterial cell wall remodeling in Bacillus cereus. Analysis of 30 Bacillus-containing probiotic products in China detected universal DON contamination (134.37-674.56 ppb). Following 10-day sublethal DON exposure (0.67 μg/mL), 75-83 % of products and their isolated B. cereus strains developed high-level resistance to last-resort gram-positive antibiotics (vancomycin, daptomycin). Mechanistically, DON-induced reactive oxygen species (ROS) bursts triggered characteristic T:A→C:G DNA mutations and significantly upregulated cell wall remodeling genes (28-50 fold). Functional validation confirmed that lrgA overexpression-a key regulator of cell wall homeostasis-elevated MICs of critical clinical antibiotics (carbapenems, cephalosporins, and daptomycin) by 32-64 fold in both B. cereus and B. subtilis. In DON-exposed swine, gut microbiota shifted toward gram-positive pathobionts (+72.7 %), enriching virulence factors (B. cereus emetic toxin cereulide, LPS) and vancomycin resistance genes (e.g., vanS +84.3 %, vanR +45.5 %) through oxidative stress-driven restructuring of mobile genetic networks (transposases/integrases). These findings establish mycotoxin-contaminated probiotics as unrecognized drivers of antibiotic resistance and virulence amplification, creating convergent evolutionary pressure that preferentially selects for resistance to last-resort gram-positive antibiotics across ecosystems.