The Repurposed Drug Disulfiram Inhibits Urease and Aldehyde Dehydrogenase and Prevents In Vitro Growth of the Oomycete Pythium insidiosum

Pythium insidiosum is an oomycete microorganism that causes a life threatening infectious disease, called pythiosis, in humans and animals. The disease has been increasingly reported worldwide. Conventional antifungal drugs are ineffective against P. insidiosum. Treatment of pythiosis requires the extensive removal of infected tissue (i.e., eye and leg), but inadequate surgery and recurrent infection often occur. A more effective treatment is needed for pythiosis patients. Drug repurposing is a promising strategy for the identification of a U.S. Food and Drug Administration-approved drug for the control of P. insidiosum. Disulfiram has been approved to treat alcoholism, but it exhibits antimicrobial activity against various pathogens. In this study, we explored whether disulfiram possesses an anti-P. insidiosum activity. A total of 27 P. insidiosum strains, isolated from various hosts and geographic areas, were susceptible to disulfiram in a dose-dependent manner. The MIC range of disulfiram against P. insidiosum (8 to 32 mg/liter) was in line with that of other pathogens. Proteogenomic analysis indicated that several potential targets of disulfiram (i.e., aldehyde dehydrogenase and urease) were present in P. insidiosum. By homology modeling and molecular docking, disulfiram can bind the putative aldehyde dehydrogenase and urease of P. insidiosum at low energies (i.e.,-6.1 and -4.0 Kcal/mol, respectively). Disulfiram diminished the biochemical activities of these enzymes. In conclusion, disulfiram can inhibit the growth of many pathogenic microorganisms, including P. insidiosum. The drug can bind and inactivate multiple proteins of P. insidiosum, which may contribute to its broad antimicrobial property. Drug repurposing of disulfiram could be a new treatment option for pythiosis.