Bactericidal activities of HMR 3647, moxifloxacin, and rifapentine against Mycobacterium leprae in mice

Implications of drug resistance in leprosy: disease course, reactions and the use of novel drugs

Leprosy remains a significant neglected tropical disease despite the goal of elimination having been achieved in various endemic nations over the past two decades. Reactional episodes complicate the disease course, resulting in deformities and disability. The main aim of treatment is to kill Mycobacterium leprae and decrease the bacterial load, which could help prevent further bacilli transmission. A major concern in breaking the chain of transmission and possibly for recurrent reactions is the role of drug-resistant bacilli. Though some data is available on the background prevalence of drug resistance in leprosy, there is a paucity of studies that look for resistance specifically in leprosy reactions. Administration of long-term steroids or immunosuppressants for chronic and recurrent responses in the presence of drug resistance has the twin effect of perpetuating the multiplication of resistant bacilli and encouraging the dissemination of leprosy. The increasing trend of prescribing second-line drugs for leprosy or type 2 reactions without prior assessment of drug resistance can potentially precipitate a severe public health problem as this can promote the development of resistance to second-line drugs as well. A comprehensive multicenter study, including drug resistance surveillance testing in cases of reactions, is necessary, along with the current measures to stop the spread of leprosy. Here, we have detailed the history of drug resistance in leprosy, given pointers on when to suspect drug resistance, described the role of resistance in reactions, methods of resistance testing, and the management of resistant cases with second-line therapy.

A Comparative Insight on the Newly Emerging Rifamycins: Rifametane, Rifalazil, TNP-2092 and TNP-2198

Rifamycins are considered a milestone for tuberculosis (TB) treatment because of their proficient sterilizing ability. Currently, available TB treatments are complicated and need a long duration, which ultimately leads to failure of patient compliance. Some new rifamycin derivatives, i.e., rifametane, TNP-2092 (rifamycin-quinolizinonehybrid), and TNP-2198 (rifamycin-nitromidazole hybrid) are under clinical trials, which are attempting to overcome the problems associated with TB treatment. The undertaken review is intended to compare the pharmacokinetics, pharmacodynamics and safety profiles of these rifamycins, including rifalazil, another derivative terminated in phase II trials, and already approved rifamycins. The emerging resistance of microbes is an imperative consideration associated with antibiotics. Resistance development potential of microbial strains against rifamycins and an overview of chemistry, as well as structure-activity relationship (SAR) of rifamycins, are briefly described. Moreover, issues associated with rifamycins are discussed as well. We expect that newly emerging rifamycins shall appear as potential tools for TB treatment in the near future.

Post-exposure prophylaxis (PEP) efficacy of rifampin, rifapentine, moxifloxacin, minocycline, and clarithromycin in a susceptible-subclinical model of leprosy

BACKGROUND

Subclinical infection with Mycobacterium leprae is one potential source of leprosy transmission, and post-exposure prophylaxis (PEP) regimens have been proposed to control this source. Because PEP trials require considerable investment, we applied a sensitive variation of the kinetic mouse footpad (MFP) screening assay to aid in the choice of drugs and regimens for clinical trials.

METHODOLOGY/PRINCIPAL FINDINGS

Athymic nude mice were inoculated in the footpad (FP) with 6 x 103 viable M. leprae and treated by gastric gavage with a single dose of Rifampin (SDR), Rifampin + Ofloxacin + Minocycline (SD-ROM), or Rifapentine + Minocycline + Moxifloxacin (SD-PMM) or with the proposed PEP++ regimen of three once-monthly doses of Rifampin + Moxifloxacin (RM), Rifampin + Clarithromycin (RC), Rifapentine + Moxifloxacin (PM), or Rifapentine + Clarithromycin (PC). At various times post-treatment, DNA was purified from the FP, and M. leprae were enumerated by RLEP quantitative PCR. A regression analysis was calculated to determine the expected RLEP value if 99.9% of the bacilli were killed after the administration of each regimen. SDR and SD-ROM induced little growth delay in this highly susceptible murine model of subclinical infection. In contrast, SD-PMM delayed measurable M. leprae growth above the inoculum by 8 months. The four multi-dose regimens delayed bacterial growth for >9months post-treatment cessation.

CONCLUSIONS/SIGNIFICANCE

The delay in discernable M. leprae growth post-treatment was an excellent indicator of drug efficacy for both early (3-4 months) and late (8-9 months) drug efficacy. Our data indicates that multi-dose PEP may be required to control infection in highly susceptible individuals with subclinical leprosy to prevent disease and decrease transmission.

WQ-3810 inhibits DNA gyrase activity in ofloxacin-resistant Mycobacterium leprae

BACKGROUND

Mycobacterium leprae causes leprosy and ofloxacin is used to control this bacterium. However, specific amino acid substitutions in DNA gyrases of M. leprae interferes with the effect of ofloxacin.

METHODOLOGY/PRINCIPAL FINDINGS

Here we tested the inhibitory effect of WQ-3810 on DNA gyrases in M. leprae, using recombinant gyrases. We theorized that WQ-3810 and DNA gyrases interacted, which was tested in silico. Compared with control drugs like ofloxacin, WQ-3810 showed a better inhibitory effect on ofloxacin-resistant DNA gyrases. The in-silico study showed that, unlike control drugs, a specific linkage between a R1 group in WQ-3810 and aspartic acid at position 464 in the subunit B of DNA gyrases existed, which would enhance the inhibitory effect of WQ-3810. This linkage was confirmed in a further experiment, using recombinant DNA gyrases with amino acid substitutions in subunits B instead.

CONCLUSIONS/SIGNIFICANCE

The inhibitory effect of WQ-3810 was likely enhanced by the specific linkage between a R1 group residue in its structure and DNA gyrases. Using interactions like the one found in the present work may help design new fluoroquinolones that contribute to halt the emergence of antibiotic-resistant pathogens.

An enhanced regimen as post-exposure chemoprophylaxis for leprosy: PEP+

The ongoing transmission of Mycobacterium (M.) leprae reflected in a very slow decline in leprosy incidence, forces us to be innovative and conduct cutting-edge research. Single dose rifampicin (SDR) as post-exposure prophylaxis (PEP) for contacts of leprosy patients, reduces their risk to develop leprosy by 60%. This is a promising new preventive measure that can be integrated into routine leprosy control programmes, as is being demonstrated in the Leprosy Post-Exposure Programme that is currently ongoing in eight countries.The limited (60%) effectiveness of SDR is likely due to the fact that some contacts have a preclinical infection beyond the early stages for which SDR is not sufficient to prevent the development of clinical signs and symptoms of leprosy. An enhanced regimen, more potent against a higher load of leprosy bacteria, would increase the effectiveness of this preventive measure significantly.The Netherlands Leprosy Relief (NLR) is developing a multi-country study aiming to show that breaking the chain of transmission of M. leprae is possible, evidenced by a dramatic reduction in incidence. In this study the assessment of the effectiveness of an enhanced prophylactic regimen for leprosy is an important component. To define the so called PEP++ regimen for this intervention study, NLR convened an Expert Meeting that was attended by clinical leprologists, public health experts, pharmacologists, dermatologists and microbiologists.The Expert Meeting advised on combinations of available drugs, with known efficacy against leprosy, as well as on the duration of the intake, aiming at a risk reduction of 80-90%. To come to a conclusion the Expert Meeting considered the bactericidal, sterilising and bacteriostatic activity of the potential drugs. The criteria used to determine an optimal enhanced regimen were: effectiveness, safety, acceptability, availability, affordability, feasibility and not inducing drug resistance.The Expert Meeting concluded that the enhanced regimen for the PEP++ study should comprise three standard doses of rifampicin 600 mg (weight adjusted when given to children) plus moxifloxacin 400 mg given at four-weekly intervals. For children and for adults with contraindications for moxifloxacin, moxifloxacin should be replaced by clarithromycin 300 mg (weight adjusted).

Leprosy: current situation, clinical and laboratory aspects, treatment history and perspective of the uniform multidrug therapy for all patients

In this review, the most relevant and current epidemiological data, the main clinical, laboratory and therapeutical aspects of leprosy are presented. Detailed discussion of the main drugs used for leprosy treatment, their most relevant adverse effects, evolution of the therapeutic regimen, from dapsone as a monotherapy to the proposed polychemotherapy by World Health Organization (WHO) can be found in this CME. We specifically highlight the drug acceptability, reduction in treatment duration and the most recent proposal of a single therapeutic regimen, with a fixed six months duration, for all clinical presentations, regardless of their classification.

Assessment of vocation of rifabutin and rifapentine in replace of rifampcin in drug resistance leprosy patients: a molecular simulation study

The emergence of drug resistance in leprosy is a major hurdle in leprosy elimination programme. Although the problem of drug resistance is presently not acute, it is important that we collect data more systematically and monitor the trend carefully so that effective measures to combat this problem can be developed. The present study aimed at the explication of cross resistance of rifabutin and rifapentine to rifampicin which would be helpful to programme managers for implementing rifabutin or rifapentine in replace of rifampicin. In this study we built 3D model of the M. leprae rpoB using Swiss Model and the modelled structure was docked with rifampicin, rifabutin and rifapentine. We established that these 3 antibiotics interact with the same binding region in the modelled rpoB of M. leprae. Thus we conclude that vocation of rifabutin and rifapentine could not be suitable in replace of rifampicin to combat with drug resistance leprosy.

Nitazoxanide is active against Mycobacterium leprae

Nitazoxanide (NTZ) is an anti-parasitic drug that also has activity against bacteria, including Mycobacterium tuberculosis. Our data using both radiorespirometry and live-dead staining in vitro demonstrate that NTZ similarly has bactericidal against M. leprae. Further, gavage of M. leprae-infected mice with NTZ at 25mg/kg provided anti-mycobacterial activity equivalent to rifampicin (RIF) at 10 mg/kg. This suggests that NTZ could be considered for leprosy treatment.

DC-159a Shows Inhibitory Activity against DNA Gyrases of Mycobacterium leprae

BACKGROUND

Fluoroquinolones are a class of antibacterial agents used for leprosy treatment. Some new fluoroquinolones have been attracting interest due to their remarkable potency that is reportedly better than that of ofloxacin, the fluoroquinolone currently recommended for treatment of leprosy. For example, DC-159a, a recently developed 8-methoxy fluoroquinolone, has been found to be highly potent against various bacterial species. Nonetheless, the efficacy of DC-159a against Mycobacterium leprae is yet to be examined.

METHODOLOGY/PRINCIPAL FINDINGS

To gather data that can support highly effective fluoroquinolones as candidates for new remedies for leprosy treatment, we conducted in vitro assays to assess and compare the inhibitory activities of DC-159a and two fluoroquinolones that are already known to be more effective against M. leprae than ofloxacin. The fluoroquinolone-inhibited DNA supercoiling assay using recombinant DNA gyrases of wild type and ofloxacin-resistant M. leprae revealed that inhibitory activities of DC-159a and sitafloxacin were at most 9.8- and 11.9-fold higher than moxifloxacin. Also the fluoroquinolone-mediated cleavage assay showed that potencies of those drugs were at most 13.5- and 9.8-fold higher than moxifloxacin. In addition, these two drugs retained their inhibitory activities even against DNA gyrases of ofloxacin-resistant M. leprae.

CONCLUSIONS/SIGNIFICANCE

The results indicated that DC-159a and sitafloxacin are more effective against wild type and mutant M. leprae DNA gyrases than moxifloxacin, suggesting that these antibacterial drugs can be good candidates that may supersede current fluoroquinolone remedies. DC-159a in particular is very promising because it is classified in a subgroup of fluoroquinolones that is known to be less likely to cause adverse effects. Our results implied that DC-159a is well worth further investigation to ascertain its in vivo effectiveness and clinical safety for humans.

Combination chemoprophylaxis and immunoprophylaxis in reducing the incidence of leprosy

Leprosy is a complex infectious disease caused by Mycobacterium leprae that is a leading cause of nontraumatic peripheral neuropathy. Current control strategies, with a goal of early diagnosis and treatment in the form of multidrug therapy, have maintained new case reports at ~225,000 per year. Diagnostic capabilities are limited and even with revisions to multidrug therapy regimen, treatment can still require up to a year of daily drug intake. Although alternate chemotherapies or adjunct immune therapies that could provide shorter or simpler treatment regimen appear possible, only a limited number of trials have been conducted. More proactive strategies appear necessary in the drive to elimination. As a prevention strategy, most chemoprophylaxis campaigns to date have provided about a 2-year protective window. Vaccination, in the form of a single bacillus Calmette–Guérin (BCG) immunization, generally provides ~50% reduction in leprosy cases. Adapting control strategies to provide both chemoprophylaxis and immunoprophylaxis has distinct appeal, with chemoprophylaxis theoretically buttressed by vaccination to generate immediate protection that can be sustained in the long term. We also discuss simple assays measuring biomarkers as surrogates for disease development or replacements for invasive, but not particularly sensitive, direct measures of M. leprae infection. Such assays could facilitate the clinical trials required to develop these new chemoprophylaxis, immunoprophylaxis strategies, and transition into wider use.

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

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.

Leprosy therapy, past and present: can we hope to eliminate it?

Leprosy remains an important problem globally. Timely detection of new cases and prompt treatment with MDT continue to be the main intervention strategies. We review the various issues related to classification, treatment, drug resistance and the possible steps to eliminate the disease in the near future. The need for newer anti leprosy agents has been felt and various agents like fluroquinolones, macrolides and minocycline have all been tried in various combinations and duration. Uniform MDT in all leprosy patients might be a logical one too. Drug resistance can be identified by PCR based DNA sequence analysis which saves much time. Drugs like thalidomide analogues, pentoxifylline, selective cytokine inhibitory drugs have proved effective in controlling type-2 reaction in leprosy patients. New drugs for leprosy reactions are still needed. Far from being eliminated as a public health problem, leprosy still causes a considerable long term morbidity in both developing and developed world. New treatment and the optimal length of MDT requires further research. We need genome based technology to address the unresolved issues of transmission of M. leprae.

Powerful bactericidal activity of moxifloxacin in human leprosy

In a clinical trial of moxifloxacin in eight multibacillary leprosy patients, moxifloxacin proved highly effective. In all trial patients, a single 400-mg dose of moxifloxacin resulted in significant killing (P Collapse

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MESH Headings

• Adult
• Animals
• Anti-Bacterial Agents/administration & dosage
• Anti-Bacterial Agents/pharmacology
• Anti-Bacterial Agents/therapeutic use
• Aza Compounds/administration & dosage
• Aza Compounds/pharmacology
• Aza Compounds/therapeutic use
• Fluoroquinolones
• Foot/microbiology
• Humans
• Leprosy/drug therapy
• Leprosy/microbiology
• Leprosy/pathology
• Male
• Mice
• Middle Aged
• Moxifloxacin
• Mycobacterium leprae/drug effects
• Mycobacterium leprae/growth & development
• Mycobacterium leprae/pathogenicity
• Quinolines/administration & dosage
• Quinolines/pharmacology
• Quinolines/therapeutic use
• Skin/microbiology
• Skin/pathology
• Treatment Outcome

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Affiliation(s)

Fe Eleanor F Pardillo Leonard Wood Memorial Center for Leprosy Research, Cebu, Philippines
Jasmin Burgos
Tranquilino T Fajardo
Eduardo Dela Cruz
Rodolfo M Abalos
Rose Maria D Paredes
Cora Evelyn S Andaya
Robert H Gelber

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Are variable-number tandem repeats appropriate for genotyping Mycobacterium leprae?

Comparative genomics analysis of the Tamil Nadu strain of Mycobacterium leprae has uncovered several polymorphic sites with potential as epidemiological tools. In this study we compared the stability of two different markers of genomic biodiversity of M. leprae in several biopsy samples isolated from the same leprosy patient. The first type comprises five different variable-number tandem repeats (VNTR), while the second is composed of three single nucleotide polymorphisms (SNP). Contrasting results were obtained, since no variation was seen in the SNP profiles of M. leprae from 42 patients from 7 different locations in Mali whereas the VNTR profiles varied considerably. Furthermore, since variation in the VNTR pattern was seen not only between different isolates of M. leprae but also between biopsy samples from the same patient, these VNTR may be too dynamic for use as epidemiological markers for leprosy.

Expression and purification of an active form of the Mycobacterium leprae DNA gyrase and its inhibition by quinolones

Mycobacterium leprae, the causative agent of leprosy, is noncultivable in vitro; therefore, evaluation of antibiotic activity against M. leprae relies mainly upon the mouse footpad system, which requires at least 12 months before the results become available. We have developed an in vitro assay for studying the activities of quinolones against the DNA gyrase of M. leprae. We overexpressed in Escherichia coli the M. leprae GyrA and GyrB subunits separately as His-tagged proteins by using a pET plasmid carrying the gyrA and gyrB genes. The soluble 97.5-kDa GyrA and 74.5-kDa GyrB subunits were purified by nickel chelate chromatography and were reconstituted as an enzyme with DNA supercoiling activity. Based on the drug concentrations that inhibited DNA supercoiling by 50% or that induced DNA cleavage by 25%, the 13 quinolones tested clustered into three groups. Analysis of the quinolone structure-activity relationship demonstrates that the most active quinolones against M. leprae DNA gyrase share the following structural features: a substituted carbon at position 8, a cyclopropyl substituent at N-1, a fluorine at C-6, and a substituent ring at C-7. We conclude that the assays based on DNA supercoiling inhibition and drug-induced DNA cleavage on purified M. leprae DNA gyrase are rapid, efficient, and safe methods for the screening of quinolone derivatives with potential in vivo activities against M. leprae.

In vitro and in vivo activities of rifampin, streptomycin, amikacin, moxifloxacin, R207910, linezolid, and PA-824 against Mycobacterium ulcerans

Seven antimicrobials were tested in vitro against 29 clinical isolates of Mycobacterium ulcerans. R207910 demonstrated the lowest MIC(50) and MIC(90), followed by moxifloxacin (MXF), streptomycin (STR), rifampin (RIF), amikacin (AMK), linezolid (LZD), and PA-824. All but PA-824 demonstrated an MIC(90) significantly less than the clinically achievable peak serum level. Administered as monotherapy to mice, RIF, STR, AMK, MXF, R207910, and LZD demonstrated some degree of bactericidal activity, whereas PA-824 failed to prevent mortality and to reduce the mean number of CFU in the footpads. Because 4 or 8 weeks of treatment by the combinations RIF-MXF, RIF-R207910, and RIF-LZD displayed bactericidal effects similar to those of RIF-STR and RIF-AMK, these three combinations might be considered as orally administered combined regimens for treatment of Buruli ulcer. Taking into account the cost, potential toxicity, and availability, the combination RIF-MXF appears more feasible for application in the field; additional experiments with mice are warranted to define further its activity against M. ulcerans. In addition, a pilot clinical trial is proposed to test the efficacy of RIF-MXF for treatment of Buruli ulcer.

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.

Leprosy and the peripheral nervous system: basic and clinical aspects

Leprosy is one of the most common causes of nontraumatic peripheral neuropathy in the developing world. The causative agent, Mycobacterium leprae, has a predilection for Schwann cells, where the organism multiplies unimpeded by organism-specific host immunity, resulting in destruction of myelin, secondary inflammatory changes, and destruction of the nerve architecture. The cardinal diagnostic features of leprosy are anesthetic skin lesions, neuropathy, and positive skin smears for the bacilli. However, patients may rarely present without skin lesions in pure neuritic leprosy. Electrodiagnostic findings early in the disease reveal demyelinating features, such as slowing of conduction velocity and prolongation of latencies, but as the disease progresses secondary axonal damage commonly ensues. Electrodiagnostic studies are also useful to monitor for toxicity secondary to therapy, particularly thalidomide-associated neuropathy. Nerve biopsy of a sensory cutaneous nerve is sometimes essential to confirm a diagnosis of leprosy. Significant advances in understanding of the pathogenesis, mapping of the genome, and other advances in molecular biology may result in better preventive and therapeutic modalities, and the goal of eradicating leprosy as a global problem may yet be realized.

Leprosy: current diagnostic and treatment approaches

PURPOSE OF REVIEW

Leprosy remains an important problem globally and leprosy patients may present to physicians outside leprosy endemic areas. We review the recent biological and clinical advances in leprosy.

RECENT FINDINGS

Sequencing the genome has been a major biological advance and will open up new possibilities for research. The three cardinal criteria (anaesthetic skin patches, thickened nerves and acid-fast bacilli in skin smears) have not yet been bettered. Multidrug therapy for leprosy is highly effective with low relapse rates though the optimal duration of therapy for multibacillary patients is unclear. Nerve damage remains a significant problem (in some series only 50% responding to steroid therapy). New treatments for leprosy reactions are needed. Stigma remains a problem but is being combated by patient groups.

SUMMARY

Far from being eliminated as a public health problem, leprosy still causes a considerable long-term morbidity in both the developing and developed world. New treatments for leprosy reactions are needed and the optimal length of multidrug therapy required further research.