Disulfiram Exhibits Potent Copper-Dependent Antimicrobial Activity Against Mycoplasma genitalium

Background: Mycoplasma genitalium (Mgen) is a sexually transmitted urogenital pathogen. Studies in sexual health clinic settings have demonstrated that Mgen infection, with similar prevalence to Chlamydia trachomatis infection, is becoming increasingly resistant to the limited classes of antibiotics with in vitro and clinical activity. Disulfiram (DS) is a Food and Drug Administration-approved drug for treatment of alcohol dependence that shows promise for repurposing as an antimicrobial agent. Methods: Minimum inhibitory concentration was performed via standard methods for human mycoplasmas and ureaplasmas as established by guideline M43-A of the Clinical and Laboratory Standards Institute. Mgen strain G37 was used as a part of a colorimetric checkboard assay to explore the mechanism of growth inhibition with DS, with emphasis on the role of copper on DS antimicrobial activity. Trace concentrations of radioactive ⁶⁴Cu were used to understand Cu²⁺ trafficking and probe the antimicrobial mechanism of DS for strain G37 and 2 DS-resistant mutants (D3 and D4). Results: DS exhibits in vitro antimicrobial activity against Mgen isolates with low minimum inhibitory concentration values, regardless of susceptibility to other antibiotics. Growth inhibition studies with DS demonstrated that antimicrobial activity is copper dependent. Studies with ⁶⁴Cu showed that DS greatly enhances copper uptake but that impaired DS-mediated copper uptake is not the mechanism for DS-resistance in Mgen mutants D3 and D4. Conclusions: DS exhibits potent copper-dependent antimicrobial activity against Mgen. DS or a similar compound could be developed as therapy for drug-resistant Mgen infections.