Fidaxomicin reduces early toxin A and B production and sporulation in Clostridium difficile in vitro

Fidaxomicin, a macrocyclic antibiotic, has been approved for the treatment of Clostridium difficile infection (CDI). Previous work by our group has demonstrated that some antibiotics at sub-inhibitory concentrations stimulate early toxin production and sporulation by C. difficile. Prior studies revealed that fidaxomicin, when added to late stationary-phase organisms, reduced exotoxin production and spore formation by C. difficile. However, the ability of fidaxomicin to trigger early virulence factor production and spore formation has never been investigated.