Structural Insights into the Quinolone Resistance Mechanism of Mycobacterium tuberculosis DNA Gyrase

Mycobacterium tuberculosis DNA gyrase, an indispensable nanomachine involved in the regulation of DNA topology, is the only type II topoisomerase present in this organism and is hence the sole target for quinolone action, a crucial drug active against multidrug-resistant tuberculosis. To understand at an atomic level the quinolone resistance mechanism, which emerges in extensively drug resistant tuberculosis, we performed combined functional, biophysical and structural studies of the two individual domains constituting the catalytic DNA gyrase reaction core, namely the Toprim and the breakage-reunion domains. This allowed us to produce a model of the catalytic reaction core in complex with DNA and a quinolone molecule, identifying original mechanistic properties of quinolone binding and clarifying the relationships between amino acid mutations and resistance phenotype of M. tuberculosis DNA gyrase. These results are compatible with our previous studies on quinolone resistance. Interestingly, the structure of the entire breakage-reunion domain revealed a new interaction, in which the Quinolone-Binding Pocket (QBP) is blocked by the N-terminal helix of a symmetry-related molecule. This interaction provides useful starting points for designing peptide based inhibitors that target DNA gyrase to prevent its binding to DNA

Analyse des coûts de chantiers en Pays de la Loire.

Analyse des coûts de chantiers en Pays de la Loire

<em>Egeria densa</em> in river Vendée in Fontenay-le-Comte (Western France): science for management

International audienc

<em>Egeria densa</em> in river Vendée in Fontenay-le-Comte (Western France): science for management

International audienc

Egeria densa in River Vendée in Fontenay-le-Comte (Western France): Science for Management

Egeria densa in River Vendée in Fontenay-le-Comte (Western France): Science for Managemen

Resistance of M. leprae to Quinolones: A Question of Relativity?

International audienceMultidrug resistant leprosy, defined as resistance to rifampin, dapsone and fluoroquinolones (FQ), has been described in Mycobacterium leprae. However, the in vivo impact of fluoroquinolone resistance, mainly mediated by mutations in DNA gyrase (GyrA 2 GyrB 2), has not been precisely assessed. Our objective was to measure the impact of a DNA gyrase mutation whose implication in fluoroquinolone resistance has been previously demonstrated through biochemical studies, on the in vivo activity of 3 fluoroquinolones: ofloxacin, moxifloxacin and garenoxacin. Methodology/Principal Findings: We used the proportional bactericidal method. 210 four-week-old immunodeficient female Nude mice (NMRI-Foxn1 nu /Foxn1 nu) were inoculated in the left hind footpad with 0.03 ml of bacterial suspension containing 5610 3 , 5610 2 , 5610 1 , and 5610 0 M. leprae AFB organisms of strain Hoshizuka-4 which is a multidrug resistant strain harboring a GyrA A91V substitution. An additional subgroup of 10 mice was inoculated with 5610 21 bacilli in the untreated control group. The day after inoculation, subgroups of mice were treated with a single dose of ofloxacin, moxifloxacin, garenoxacin or clarithromycin at 150 mg/kg dosing. 12 months later mice were sacrificed and M. leprae bacilli were numbered in the footpad. The results from the untreated control group indicated that the infective inoculum contained 23% of viable M. leprae. The results from the moxifloxacin and garenoxacin groups indicated that a single dose of these drugs reduced the percentage of viable M. leprae by 90%, similarly to the reduction observed after a single dose of the positive control drug clarithromycin. Conversely, ofloxacin was less active than clarithromycin. Conclusion/Significance: DNA gyrase mutation is not always synonymous of lack of in vivo fluoroquinolone activity in M. leprae. As for M. tuberculosis, in vivo studies allow to measure residual antibiotic activity in case of target mutations in M. leprae

Les plateformes PREVENIR (PREVention ENvIronnement Reproduction) : plateformes de prévention en santé environnement dédiées à la reproduction

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Les plateformes PREVENIR (PREVention ENvIronnement Reproduction) : plateformes de prévention en santé environnement dédiées à la reproduction

International audienc