Minimal effective dose of bedaquiline administered orally and activity of a long acting formulation of bedaquiline in the murine model of leprosy.

BACKGROUND: Bedaquiline (BDQ), by targeting the electron transport chain and having a long half-life, is a good candidate to simplify leprosy treatment. Our objectives were to (i) determine the minimal effective dose (MED) of BDQ administered orally, (ii) evaluate the benefit of combining two inhibitors of the respiratory chain, BDQ administered orally and clofazimine (CFZ)) and (iii) evaluate the benefit of an intramuscular injectable long-acting formulation of BDQ (intramuscular BDQ, BDQ-LA IM), in a murine model of leprosy. METHODOLOGY/PRINCIPAL FINDINGS: To determine the MED of BDQ administered orally and the benefit of adding CFZ, 100 four-week-old female nude mice were inoculated in the footpads with 5x103 bacilli of M. leprae strain THAI53. Mice were randomly allocated into: 1 untreated group, 5 groups treated with BDQ administered orally (0.10 to 25 mg/kg), 3 groups treated with CFZ 20 mg/kg alone or combined with BDQ administered orally 0.10 or 0.33 mg/kg, and 1 group treated with rifampicin (RIF) 10 mg/kg. Mice were treated 5 days a week during 24 weeks. To evaluate the benefit of the BDQ-LA IM, 340 four-week-old female swiss mice were inoculated in the footpads with 5x103 to 5x101 bacilli (or 5x100 for the untreated control group) of M. leprae strain THAI53. Mice were randomly allocated into the following 11 groups treated with a single dose (SD) or 3 doses (3D) 24h after the inoculation: 1 untreated group, 2 treated with RIF 10 mg/kg SD or 3D, 8 treated with BDQ administered orally or BDQ-LA IM 2 or 20 mg/kg, SD or 3D. Twelve months later, mice were sacrificed and M. leprae bacilli enumerated in the footpad. All the footpads became negative with BDQ at 3.3 mg/kg. The MED of BDQ administered orally against M. leprae in this model is therefore 3.3 mg/kg. The combination of CFZ and BDQ 10-fold lower than this MED did not significantly increase the bactericidal activity of CFZ. The BDQ-LA IM displayed similar or lower bactericidal activity than the BDQ administered orally. CONCLUSION: We demonstrated that the MED of BDQ administered orally against M. leprae was 3.3 mg/kg in mice and BDQ did not add significantly to the efficacy of CFZ at the doses tested. BDQ-LA IM was similar or less active than BDQ administered orally at equivalent dosing and frequency but should be tested at higher dosing in order to reach equivalent exposure in further experiments.

A systematic review of Mycobacterium leprae DNA gyrase mutations and their impact on fluoroquinolone resistance.

BACKGROUND: The fact that Mycobacterium leprae does not grow in vitro remains a challenge in the survey of its antimicrobial resistance (AMR). Mainly molecular methods are used to diagnose AMR in M. leprae to provide reliable data concerning mutations and their impact. Fluoroquinolones (FQs) are efficient for the treatment of leprosy and the main second-line drugs in case of multidrug resistance. OBJECTIVES: This study aimed at performing a systematic review (a) to characterize all DNA gyrase gene mutations described in clinical isolates of M. leprae, (b) to distinguish between those associated with FQ resistance or susceptibility and (c) to delineate a consensus numbering system for M. leprae GyrA and GyrB. DATA SOURCES: Data source was PubMed. STUDY ELIGIBILITY CRITERIA: Publications reporting genotypic susceptibility-testing methods and gyrase gene mutations in M. leprae clinical strains. RESULTS: In 25 studies meeting our inclusion criteria, 2884 M. leprae isolates were analysed (2236 for gyrA only (77%) and 755 for both gyrA and gyrB (26%)): 3.8% of isolates had gyrA mutations (n = 110), mostly at position 91 (n = 75, 68%) and 0.8% gyrB mutations (n = 6). Since we found discrepancies regarding the location of substitutions associated with FQ resistance, we established a consensus numbering system to properly number the mutations. We also designed a 3D model of the M. leprae DNA gyrase to predict the impact of mutations whose role in FQ-susceptibility has not been demonstrated previously. CONCLUSIONS: Mutations in DNA gyrase are observed in 4% of the M. leprae clinical isolates. To solve discrepancies among publications and to distinguish between mutations associated with FQ resistance or susceptibility, the consensus numbering system we proposed as well as the 3D model of the M. leprae gyrase for the evaluation of the impact of unknown mutations in FQ resistance, will provide help for resistance surveillance.

Population Genomics of Mycobacterium leprae Reveals a New Genotype in Madagascar and the Comoros.

Human settlement of Madagascar traces back to the beginning of the first millennium with the arrival of Austronesians from Southeast Asia, followed by migrations from Africa and the Middle East. Remains of these different cultural, genetic, and linguistic legacies are still present in Madagascar and other islands of the Indian Ocean. The close relationship between human migration and the introduction and spread of infectious diseases, a well-documented phenomenon, is particularly evident for the causative agent of leprosy, Mycobacterium leprae. In this study, we used whole-genome sequencing (WGS) and molecular dating to characterize the genetic background and retrace the origin of the M. leprae strains circulating in Madagascar (n = 30) and the Comoros (n = 3), two islands where leprosy is still considered a public health problem and monitored as part of a drug resistance surveillance program. Most M. leprae strains (97%) from Madagascar and Comoros belonged to a new genotype as part of branch 1, closely related to single nucleotide polymorphism (SNP) type 1D, named 1D-Malagasy. Other strains belonged to the genotype 1A (3%). We sequenced 39 strains from nine other countries, which, together with previously published genomes, amounted to 242 genomes that were used for molecular dating. Specific SNP markers for the new 1D-Malagasy genotype were used to screen samples from 11 countries and revealed this genotype to be restricted to Madagascar, with the sole exception being a strain from Malawi. The overall analysis thus ruled out a possible introduction of leprosy by the Austronesian settlers and suggests a later origin from East Africa, the Middle East, or South Asia.

New Insights into the Geographic Distribution of Mycobacterium leprae SNP Genotypes Determined for Isolates from Leprosy Cases Diagnosed in Metropolitan France and French Territories.

BACKGROUND: Between 20 and 30 bacteriologically confirmed cases of leprosy are diagnosed each year at the French National Reference Center for mycobacteria. Patients are mainly immigrants from various endemic countries or living in French overseas territories. We aimed at expanding data regarding the geographical distribution of the SNP genotypes of the M. leprae isolates from these patients. METHODOLOGY/PRINCIPAL FINDINGS: Skin biopsies were obtained from 71 leprosy patients diagnosed between January 2009 and December 2013. Data regarding age, sex and place of birth and residence were also collected. Diagnosis of leprosy was confirmed by microscopic detection of acid-fast bacilli and/or amplification by PCR of the M. leprae-specific RLEP region. Single nucleotide polymorphisms (SNP), present in the M. leprae genome at positions 14 676, 1 642 875 and 2 935 685, were determined with an efficiency of 94% (67/71). Almost all patients were from countries other than France where leprosy is still prevalent (n = 31) or from French overseas territories (n = 36) where leprosy is not totally eradicated, while only a minority (n = 4) was born in metropolitan France but have lived in other countries. SNP type 1 was predominant (n = 33), followed by type 3 (n = 17), type 4 (n = 11) and type 2 (n = 6). SNP types were concordant with those previously reported as prevalent in the patients' countries of birth. SNP types found in patients born in countries other than France (Comoros, Haiti, Benin, Congo, Sri Lanka) and French overseas territories (French Polynesia, Mayotte and La Réunion) not covered by previous work correlated well with geographical location and history of human settlements. CONCLUSIONS/SIGNIFICANCE: The phylogenic analysis of M. leprae strains isolated in France strongly suggests that French leprosy cases are caused by SNP types that are (a) concordant with the geographic origin or residence of the patients (non-French countries, French overseas territories, metropolitan France) or (b) more likely random in regions where diverse migration flows occurred.

Resistance of M. leprae to quinolones: a question of relativity?

UNLABELLED: Multidrug 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 (GyrA2GyrB2), 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 5 × 10(3), 5 × 10(2), 5 × 10(1), and 5 × 10(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 5 × 10(-1) 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.

Bactericidal activities of R207910 and other newer antimicrobial agents against Mycobacterium leprae in mice.

As measured by a proportional bactericidal technique in the mouse footpad system, the bactericidal activity against Mycobacterium leprae of R207910 was equal to that of rifapentine, rifampin, or moxifloxacin and significantly greater than those of minocycline, PA-824, and linezolid. These data suggest that R207910 may play an important role in treatment of leprosy.

Dihydropteroate synthase mutations in the folP1 gene predict dapsone resistance in relapsed cases of leprosy.

Molecular detection was compared with the mouse footpad inoculation test for detection of dapsone resistance in 38 strains of Mycobacterium leprae. Mutations of the folP1 gene (at codons 53 or 55) were found in 6 of 6 strains with high-level resistance, in 3 of 4 strains with intermediate-level resistance, and in 1 of 6 strains with low-level resistance, but not in 22 dapsone-susceptible strains. In cases of infection with strains of M. leprae carrying the folP1 mutation, therapy with dapsone may be replaced by therapy with a fluoroquinolone.