The antimycobacterial activities of disulfiram (DSF) and diethyldithiocarbamate (DDC) against multidrug-and extensively drug-resistant tuberculosis (MDR/XDR-TB) clinical isolates were evaluated in vitro. Both DSF and DDC exhibited potent antitubercular activities against 42 clinical isolates of M. tuberculosis, including MDR/XDR-TB strains. Moreover, DSF showed remarkable bactericidal activity ex vivo and in vivo. Therefore, DSF might be a drug repurposed for the treatment of MDR/XDR-TB.
According to the updated guidelines of the World Health Organization, the medications effective against multidrug-and extensively drug-resistant tuberculosis (MDR/XDR-TB) are confined because only a limited selection of drugs is available; therefore, the development of novel or repurposed drugs with activity against MDR/XDR-TB is strongly desired (9). Disulfiram (DSF; tetraethyl thiuram disulfide) has been used orally in the clinical treatment of alcoholism since 1949 and has been proven to exert an inhibitory effect on aldehyde dehydrogenase in vivo with 80% bioavailability and established safety profiles (13, 33). Both DSF and its first metabolite, diethyldithiocarbamate (DDC), were reported to exhibit growth-inhibitory activity against bacteria, fungi, protozoa, and viruses (2,18,23,26,27). In the mid-1950s, the tuberculostatic effects of DSF and DDC were demonstrated in vivo using guinea pigs (17). Subsequently, it was reported that DDC enhances monocyte-induced antitubercular activity in both healthy volunteers and human immunodeficiency virus-infected patients ex vivo (16). Recently, the antitubercular activities of DDC and the nitric oxide synthase inhibitor pyrrolidine dithiocarbamate (PDTC) against nonreplicating Mycobacterium tuberculosis have been demonstrated (4). In addition, we reported the unique antimycobacterial activities of dithiocarbamates and also the potent antitubercular activities of compounds containing dithiocarbamate groups, such as dimethyldithiocarbamate (DMDC), DDC, and PDTC (14,15). More recently, the mode of action of dithiocarbamates against M. tuberculosis has been reported to be through -class carbonic anhydrases (-CAs), which are considered possible drug targets (19). However, the mechanism of action of DSF remains unknown.In the present study, we evaluated the antimycobacterial activities of DSF and its metabolites against M. tuberculosis, including MDR/XDR-TB clinical isolates, in more detail. Furthermore, the intracellular bactericidal activities of these compounds against a virulent strain, M. tuberculosis H 37 Rv, within macrophages were examined ex vivo, and the bactericidal activity of DSF in vivo was determined using the mouse model of chronic TB. Finally, the mechanisms of action of these compounds were investigated by means of gene-overexpressing strains in vitro.
MATERIALS AND METHODSBacterial strains. M. tuberculosis H 37 Rv ATCC 25618, M. tuberculosis H 37 Ra ATCC 25177, Mycobacterium avium ATCC 25291, and M. avium ATCC 35718 were purchased from the American Type Culture Collect...