RESUMO
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 CuSO4 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 Cu2+, to determine compound MICs. RESULTS: Ureaplasma species and Mh were able to tolerate 30-60 µM CuSO4, while Mpn tolerated over 10-fold higher concentrations (>1 mM). GTSM inhibited growth of all four organisms, but was unaffected by Cu2+ 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 CuSO4 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.
RESUMO
BACKGROUND: Premature rupture of membranes and preterm delivery are associated with Ureaplasma infection. We hypothesized that Ureaplasma induced extracellular collagen fragmentation results in production of the tripeptide PGP (proline-glycine-proline), a neutrophil chemoattractant. PGP release from collagen requires matrix metalloproteases (MMP-8/MMP-9) along with a serine protease, prolyl endopeptidase (PE). METHODS: Ureaplasma culture negative amniotic fluid (indicated preterm birth, n = 8; spontaneous preterm birth, n = 8) and Ureaplasma positive amniotic fluid (spontaneous preterm birth, n = 8) were analyzed by electro-spray ionization-liquid chromatography tandem mass spectrometry for PGP, and for MMP-9 by zymography. PE was evaluated in lysates of U. parvum serovar 3 (Up3) and U. urealyticum serovar 10 (Uu10) by western blotting and activity assay. RESULTS: PGP and MMP-9 were increased in amniotic fluid from spontaneous preterm birth with positive Ureaplasma cultures, but not with indicated preterm birth or spontaneous preterm birth with negative Ureaplasma cultures. Human neutrophils cocultured with Ureaplasma strains showed increased MMP-9 activity. PE presence and activity were noted with both Ureaplasma strains. CONCLUSION: Ureaplasma spp. carry the protease necessary for PGP release, and PGP and MMP-9 are increased in amniotic fluid during Ureaplasma infection, suggesting Ureaplasma spp. induced collagen fragmentation contributes to preterm rupture of membranes and neutrophil influx causing chorioamnionitis.
