In vitro antimycobacterial spectrum of a diarylquinoline ATP synthase inhibitor.
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ABSTRACT:
SUBMITTER: Huitric E
PROVIDER: S-EPMC2151410 | biostudies-literature | 2007 Nov
REPOSITORIES: biostudies-literature
Publications
In vitro antimycobacterial spectrum of a diarylquinoline ATP synthase inhibitor.
Huitric Emma E Verhasselt Peter P Andries Koen K Hoffner Sven E SE
Antimicrobial agents and chemotherapy 20070820 11
The diarylquinoline R207910 is in clinical development for tuberculosis treatment. The MIC(50) for 41 drug-susceptible and 44 multidrug-resistant Mycobacterium tuberculosis clinical isolates was 0.032 microg/ml. Out of 20 additional mycobacterial species, three were found to be naturally resistant to R207910 and were shown to exhibit a polymorphism in their atpE genes. ...[more]
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Project description:R207910 (also known as TMC207) is an investigational drug currently in clinical studies for the treatment of multidrug-resistant (MDR) tuberculosis. It has a high degree of antimycobacterial activity and is equally effective against drug-susceptible and MDR Mycobacterium tuberculosis isolates. In the present study, we characterized the development of resistance to R207910 in vitro. Ninety-seven independent R207910-resistant mutants were selected from seven different clinical isolates of M. tuberculosis (three drug-susceptible and four MDR isolates) at 10x, 30x, and 100x the MIC. At a concentration of 0.3 mg/liter (10x the MIC), the mutation rates ranged from 4.7 x 10(-7) to 8.9 x 10(-9) mutations per cell per division, and at 1.0 mg/liter (30x the MIC) the mutation rate ranged from 3.9 x 10(-8) to 2.4 x 10(-9). No resistant mutants were obtained at 3 mg/liter (100x the MIC). The level of resistance ranged from 0.12 to 3.84 mg/liter for the mutants identified; these concentrations represent 4- to 128-fold increases in the MICs. For 53 of the resistant mutants, the atpE gene, which encodes a transmembrane and oligomeric C subunit of the ATP synthase and which was previously shown to be involved in resistance, was sequenced. For 15/53 mutants, five different point mutations resulting in five different amino acid substitutions were identified in the atpE gene. For 38/53 mutants, no atpE mutations were found and sequencing of the complete F0 ATP synthase operon (atpB, atpE, and atpF genes) and the F1 ATP synthase operon (atpH, atpA, atpG, atpD, and atpC genes) from three mutants revealed no mutations, indicating other, alternative resistance mechanisms. Competition assays showed no measurable reduction in the fitness of the mutants compared to that of the isogenic wild types.
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Project description:Despite the remarkable advances due to the discovery and development of antimicrobials agents, infectious diseases remain the second leading cause of death worldwide. This fact underlines the importance of developing new therapeutic strategies to address the widespread antibiotic resistance, which is the major contributing factor for clinical failures of the current therapeutics. In a screen for antibiotic adjuvants, we identified a natural product from actinomycetes, venturicidin A (VentA), that potentiates the aminoglycoside antibiotic gentamicin against multidrug-resistant clinical isolates of Staphylococcus, Enterococcus, and Pseudomonas aeruginosa. Furthermore, the combination of gentamicin and VentA was bactericidal and rapidly eradicated methicillin-resistant S. aureus (MRSA). The molecular mechanism of gentamicin potentiation activity is attributed to uncoupling of ATP synthesis by VentA from electron transport presumably by blocking the proton flow through ATP synthase, which results in an elevated concentration of extracellular protons and subsequent anticipated raise in gentamicin uptake. The disruption of the proton flux was characterized by perturbed membrane potential in MRSA. These results demonstrate that inhibition of ATP synthase along with the subsequent membrane dysregulation, as shown here with VentA, complements aminoglycoside antibiotics against MDR bacteria, and that this approach may be employed to combat bacterial resistance.
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