Aurodox inhibits type III secretion in multiple Gram-negative pathogens

Gram-negative pathogens pose a significant threat due to their propensity for causing various infections, often coupled with formidable resistance to conventional antibiotic treatments. The development of antivirulence (AV) compounds emerges as a promising alternative strategy by disrupting virulence mechanisms rather than targeting bacterial viability. Aurodox has exhibited promising AV properties in previous studies by blocking the expression and function of the LEE-encoded type 3 secretion system (T3SS) in enterohaemorrhagic Escherichia coli, an injectosome that translocates effector proteins directly into host target cells. However, aurodox's efficacy against the T3SS of other pathogens remained unanswered. Using quantitative real-time polymerase chain reaction, we show that aurodox exerts inhibitory effects on selected T3SS including those of Salmonella Typhimurium, Yersinia pseudotuberculosis and Vibrio parahaemolyticus. Imaging of RAW 264.7 cells infected with S. Typhimurium showed that aurodox protects against late stages of infection by blocking the expression of the SPI-2 T3SS. To elucidate a conserved mechanism of action, we compared transcriptomic datasets from both E. coli and S. Typhimurium treated with aurodox to identify orthologous genes differentially expressed in response to aurodox treatment across both pathogens. This study sheds light on potential mechanisms driving the action of this promising AV compound.