Antivirulence DsbA inhibitors attenuate serovar Typhimurium fitness without detectable resistance.

Inhibition of the DiSulfide Bond (DSB) oxidative protein folding machinery, a major facilitator of virulence in Gram-negative bacteria, represents a promising antivirulence strategy. We previously developed small molecule inhibitors of DsbA from K-12 (EcDsbA) and showed that they attenuate virulence of Gram-negative pathogens by directly inhibiting multiple diverse DsbA homologues. Here we tested the evolutionary robustness of DsbA inhibitors as antivirulence antimicrobials against serovar Typhimurium under pathophysiological conditions in vitro. We show that phenylthiophene DsbA inhibitors slow . Typhimurium growth in minimal media, phenocopying . Typhimurium isogenic null mutants. Through passaging experiments, we found that DsbA inhibitor resistance was not induced under conditions that rapidly induced resistance to ciprofloxacin, an antibiotic commonly used to treat infections. Furthermore, no mutations were identified in the gene of inhibitor-treated . Typhimurium, and . Typhimurium virulence remained susceptible to DsbA inhibitors. Our work demonstrates that under in vitro pathophysiological conditions, DsbA inhibitors can have both antivirulence and antibiotic action. Importantly, our finding that DsbA inhibitors appear to be evolutionarily robust offers promise for their further development as next-generation antimicrobials against Gram-negative pathogens.