Differential Susceptibility of Mycoplasma and Ureaplasma Species to Compound-Enhanced Copper Toxicity

Abstract

Rationale Mycoplasmas represent important etiologic agents of many human diseases. Due to increasing antimicrobial resistance and slow rate of novel discovery, unconventional methods of drug discovery are necessary. Copper ions are utilized in host microbial killing, and bacteria must regulate intracellular Cu concentrations to avoid toxicity. We hypothesized that human mollicutes may have susceptibility to Cu-induced toxicity, and compounds that augment copper-dependent killing. Methods Mycoplasma pneumoniae (Mpn), Ureaplasma parvum (Up), Ureaplasma urealyticum (Uu), and Mycoplasma hominis (Mh) were exposed to CuSO 4 to determine minimal inhibitory concentrations (MICs). Once inhibitory concentrations had been determined, bacteria were treated with an FDA-approved drug disulfiram (DSF), glyoxal bis(4-methyl-3-thiosemicarbazone) (GTSM), and 2,9-dimethyl-1,10-phenanthroline (neocuproine), with or without Cu 2+ , to determine compound MICs. Results Ureaplasma species and Mh were able to tolerate 30–60 μM CuSO 4 , while Mpn tolerated over 10-fold higher concentrations (>1 mM). GTSM inhibited growth of all four organisms, but was unaffected by Cu 2+ addition. Inhibition by GTSM was reduced by addition of the cell-impermeant Cu chelator, bathocuproine disulfonate (BCS). Neocuproine exhibited Cu-dependent growth inhibition of all organisms. DSF exhibited Cu-dependent growth inhibition against Mh at low micromolar concentrations, and at intermediate concentrations for Mpn. Conclusion MICs for CuSO 4 differ widely among human mollicutes, with higher MICs for Mpn compared to Mh, Uu, and Up. DSF and Neocuproine exhibit Cu-dependent inhibition of mollicutes with copper concentrations between 25 and 50 μM. GTSM has copper-dependent anti-microbial activity at low levels of copper. Drug enhanced copper toxicity is a promising avenue for novel therapeutic development research with Mycoplasma and Ureaplasma species.

Mycoplasma genitalium Biofilms Contain Poly-GlcNAc and Contribute to Antibiotic Resistance

“…To control for minute ethanol concentrations in Ery preparations, 50 µl of ethanol was added per 2 mL of SP4 for "EtOH control" wells. Biofilms were then incubated for 2 days until harvesting for imaging or growth index analysis as described previously (Feng et al, 2018;Totten et al, 2019). In brief, the medium was analyzed by determining OD 430/OD 560 for each condition and data were plotted as described.…”

Demonstration of N , N -Dimethyldithiocarbamate as a Copper-Dependent Antibiotic against Multiple Upper Respiratory Tract Pathogens

“…While Cu itself is toxic, 8-hydroxyquinoline (8HQ) and related chelators can function as ionophores, overwhelming cells with Cu ( 19 – 25 ). FDA-approved drugs such as disulfiram also show potent copper-dependent toxicity (CDT) ( 24 , 26 – 31 ). In this study, we report the effects of several small molecules’ activities on the growth and viability of S. pneumoniae in the presence or absence of copper.…”

In vitro and in vivo evaluation of diethyldithiocarbamate with copper ions and its liposomal formulation for the treatment of Staphylococcus aureus and Staphylococcus epidermidis biofilms

“…While Cu(DDC) 2 showed in vitro activity against Mycobacteria [ 25 ], Streptococci [ 30 , 72 ], and Mycoplasma [ 73 ], the antibacterial effects have yet to be confirmed in animal models. In contrast, the research on Cu(DDC) 2 as cancer treatment has progressed to in vivo experiments and first clinical trials.…”