Journal of Preventive, Diagnostic and Treatment Strategies in Medicine

REVIEW STRATEGY
Year
: 2022  |  Volume : 1  |  Issue : 1  |  Page : 21--25

Potential approaches for the diagnosis and treatment of drug-resistant leprosy


Mallika Lavania1, Gaurav Datta2, Umesh Dutt Gupta3,  
1 Stanley Browne Laboratory, The Leprosy Mission Community Hospital, Nand Nagri, New Delhi; Enteric Viruses Group, ICMR-National Institute of Virology, Pune, Maharashtra, India
2 Department of Medicine, Base Hospital Delhi Cantt, New Delhi, India
3 Indian Council of Medical Research, National JALMA Institute for Leprosy & Other Mycobacterial Diseases (ICMR), Tajganj, Agra, India

Correspondence Address:
Umesh Dutt Gupta
Indian Council of Medical Research,National JALMA Institute for Leprosy & Other Mycobacterial Diseases (ICMR), Tajganj, Agra
India

Abstract

Leprosy, a chronic human disease with potentially debilitating neurological consequences, results from infection with Mycobacterium leprae, which is still a major health problem in several countries of Asia, Latin America, and Africa. With the mass campaigns, using multidrug therapy, the prevalence of leprosy has come down drastically worldwide. Antimicrobial resistance (AMR) is an important consideration in the management of leprosy. Unfortunately, quinolone-resistant strains of Mycobacterium leprae have also been reported in several countries, probably due to the extensive use of quinolones for treating several types of infections. To meet the challenge of containing the disease and being able to respond to an increase in circulation of drug-resistant strains, it is essential to assess drug-sensitivity patterns globally, as well as to monitor resistance among both new and retreatment cases. However, these studies highlight the need for increased vigilance to AMR. In this study, we thoroughly reviewed the molecular methods used to detect drug resistance in leprosy. We can infer that our article assessing strategies less complex than multifunction peripheral and genome sequencing are promising choices for the testing of AMR in leprosy patients. Furthermore, our analysis recommends that the extent of safe cases has not essentially expanded in late many years.



How to cite this article:
Lavania M, Datta G, Gupta UD. Potential approaches for the diagnosis and treatment of drug-resistant leprosy.J Prev Diagn Treat Strategies Med 2022;1:21-25


How to cite this URL:
Lavania M, Datta G, Gupta UD. Potential approaches for the diagnosis and treatment of drug-resistant leprosy. J Prev Diagn Treat Strategies Med [serial online] 2022 [cited 2022 Jun 27 ];1:21-25
Available from: http://www.jpdtsm.com/text.asp?2022/1/1/21/340553


Full Text



 Introduction



To treat infectious diseases, lifestyle disorders; effective medications were developed to create a disease-free world. Leprosy: a chronic disease, which is caused by an obligate intracellular pathogen Mycobacterium leprae, is still a major health problem in several countries of Asia, Latin America, and Africa.[1],[2],[3],[4] Before the introduction of antibiotics, chaulmoogra oil was used to treat leprosy with some success. Since 1940, dapsone was the only chemotherapeutic agent used for the treatment of leprosy for about three decades. Prolonged, interrupted, and inadequate use of dapsone monotherapy leads to the development of dapsone-resistant cases. Currently, leprosy control is mainly based on the World Health Organization (WHO)-recommended multidrug therapy (MDT) which is in use in the control program for the last 30 years. Multidrug therapy is a combination of dapsone, rifampin, and clofazi–mine.[1],[2],[3],[5] With the mass campaigns, using MDT, the prevalence of leprosy has come down drastically worldwide. The prevalence rate of leprosy is declining in India but not rapidly enough. In 2019–2020, 114,451 new leprosy cases were detected in the country, which accounts for 80% of the cases of South-east Asian countries and 56.6% of the global new cases of leprosy. The states, which contributed more than 76% of the new leprosy cases, are: Bihar, Maharashtra, Uttar Pradesh, Odisha, Chhattisgarh, Madhya Pradesh, West Bengal, and Jharkhand. It has been noted earlier with any therapeutic control measure of disease with antibiotics that it leads to the emergence of drug resistance.[4],[6],[7],[8],[9],[10],[11],[12],[13],[14]

Drug resistance or unresponsiveness to any drug therapy is indicated by the reduction in the effectiveness of a medication in curing a disease or condition. The term is used in the context of resistance that pathogens have “acquired” meaning thereby resistance has been evolved in the pathogen. Hence, the development of antimicrobial resistance (AMR) by the pathogen challenges clinical care and drive research. A mono-resistant organism becomes resistant to one drug; however, a multidrug-resistant organism will acquire resistance to more than one drug.[15] Therefore, a surveillance mechanism should function as a surveillance mechanism for the appearance of drug resistance in the community. If this emergence of mutation is not checked with implementation with altered drug regimen then control measure with chemotherapy will be completely defeated.

 Standard Treatment



In India, the recommended regimen by the National Leprosy Eradication Program (NLEP) involves a 12 months' duration of treatment and excludes clofazamine in paucibacillary leprosy treatment [Table 1].{Table 1}

From 1993 onward, gene sequencing (GSEQ) has been done for M. leprae strains known to be resistant in mouse footpad experiments and isolated from cases with treatment failure. Studies showed that some missense mutations confer resistance to dapsone (mutation in the folP1 gene), rifampicin (mutation in the rpoB gene) and quinolones (mutation in the gyrA gene). The WHO has to initiate the surveillance with the objective to determine primarily resistance to rifampicin among leprosy cases, either alone or combined with resistance to dapsone and/or ofloxacin among new cases (for primary resistance) and among retreatment cases (for secondary resistance) and to monitor the resistance rates over time. If the bacteriological index of the patient is not going down, not responding to treatment, inadequate treatment and relapse will be tested for AMR testing.

Prior to the introduction of MDT, patients were treated with dapsone monotherapy for several years. Resistance to dapsone has been reported since the early 1960s. In case of resistance to rifampicin, fluoroquinolones become the preferred category of second-line drugs. Unfortunately, quinolone-resistant strains of Mycobacterium leprae have also been reported in several countries, probably due to the extensive use of quinolones for treating several types of infections. Clofazimine resistance is still rare, but this antimicrobial cannot be given alone. To meet the challenge of containing the disease and being able to respond to an increase in the circulation of drug-resistant strains, it is essential to assess drug-sensitivity patterns globally, as well as to monitor resistance among both new and retreatment cases [Figure 1].{Figure 1}

 Molecular diagnosis of Antimicrobial resistance testing



The clinical criteria and skin smears were the only methods of monitoring AMR in leprosy until the first half of the 20th century. Due to delay in the reporting period, there was an urgent need for rapid alternative methods for therapeutic decisions. From 1993 onward, GSEQ has been evaluated against clinical criteria and the multifunction peripheral (MFP) test [Figure 2].{Figure 2}

 Mouse foot pad



Leprosy presents a very special problem for detecting drug resistance because M. leprae cannot be cultured axenically. Accordingly, drug-susceptibility testing was nonexistent until 1962 when Shepard developed the MFP assay for determining M. leprae's susceptibility to anti-leprosy drugs.[16] Since its development, the MFP assay has been the “gold standard” for leprosy drug susceptibility testing. This method requires the recovery of a sufficient number of viable organisms from a patient to inoculate the footpads of 20 − 40 mice (depending on the number of drugs to be tested) with each footpad receiving 5000 − 10,000 organisms. Infected mice are treated with the appropriate drugs orally. Mice are sacrificed after a defined period (usually 6 months or longer) and the numbers of bacilli in the footpads of treated mice and untreated mice are compared. This method is cumbersome, time-consuming; results are usually available only after 6–12 months, expensive and require highly skilled laboratory staff.

 Mutation Detection by Polymerase Chain Reaction-DNA Sequencing



Drug susceptibility testing by the mouse footpad is cumbersome and time-consuming. MFP method is not applicable, to many strains and not able to obtain comprehensive data to monitor the global level of resistance. The method requires bacilli scrapped from an active lesion or ear lobes in 70% ethanol vial and transported to laboratory for DNA extraction. The drug mutations lie in one or several codons located within short stretches of DNA in each target gene, referred to as the drug resistance determining regions (DRDRs). Further DRDRs are amplified by polymerase chain reaction (PCR) targeting genes rpoB, folP, and gyrA responsible for drug rifampicin, dapsone, and ofloxacin, respectively. PCR amplified product is sequenced. Samples with known missense mutations within a limited region in these genes are checked. Globally, researchers are using this method for mutation detection.[6],[12],[17],[18],[19],[20]

 Probes Based Drug Susceptibility Testing



Analysis of mutations is generally performed by sequencing the target genomic region, amplified by PCR, although the implementation of sequencing is not easy in many developing countries. Therefore, a simple and rapid method which can be carried out without any special equipment such as sequencer has been developed. In microarray, a series of oligonucleotides probes corresponding to each mutation detected in the folP, rpoB, and gyrA genes was selected, fixed on glass slide as capture probes. Probes hybridized with the denatured samples of leprosy patients and further result analyzed in the form of dots/signals on slides.[21]

Another method GenoType LepraeDR is also introduced. Probes to capture wild type and mutants are coated on the strip. PCR products for the above-mentioned genes are amplified, denatured and then hybridized and coloration is performed.

 Real-Time Polymerase Chain Reaction-based High-Resolution Melting Analysis



Real-time PCR–high-resolution melt (PCR-HRM) analysis is a novel simple post-PCR step that exploits thermal characteristics of the amplicons for the detection of sequence variants. Emerging real-time PCR technologies that can eliminate post-PCR procedures for genotyping any M. leprae genomic target of interest, particularly those suitable for leprosy epidemiology applications. In HRM analysis, amplified DNA is denatured in precise temperature increments to produce melt curves with features that are dependent upon nucleotide sequence. Curves with similar shapes are derived from the same DNA sequence and can be clustered together, allowing researchers to analyze genetic variants post-PCR. This technique proved inexpensive and convenient for the preliminary screening of DNAs and rapid classification of clinical strains into wild-type or variant clusters, which carry some of the known mutations in the DRDRs.[22]

 Next Generation Sequencing



This era of the new age of genome sequencing began to revolutionize our strategies for human diseases, including leprosy. In the year 2000, Cole et al. reported the complete genome sequence of the M. leprae reference strain TN, which was approximately 3.27 million base pairs in length and encoded approximately 1605 protein genes.[23] In the last 20 years, next-generation sequencing (NGS) focused on both laboratory aspects of drug-resistant M. leprae.[24] NGS technology has provided a more complete account of the genomic features that cause treatment resistance, enabling the identification of novel resistance mechanisms for existing drugs, and therefore the determination of the mechanisms of action of newly discovered drugs. By using this technique, we can distinguish between relapse and reinfection[25] and as well as the role of compensatory mutations in resistant leprosy cases.[11] For sequencing purposes, DNA can be extracted from human skin biopsies of known BI using the following customized protocol that removes most of the host DNA, followed by lysis of the bacteria and purification of M. leprae DNA on silica columns.

 Management of Resistant Leprosy



AMR is an important consideration in the management of leprosy. Drug susceptibility-based studies are now performed in highly specialized laboratories using genotypic molecular techniques as well as laboratory equipped with animal testing facilities. Recently, a prospective survey obtaining data from endemic countries describes a global resistance rate of 8% from the years 2009–2015 among nearly 2000 reported cases.[10] Among these cases, 74 showed resistance to rifampicin, 87 to dapsone, and 21 to ofloxacin. Multidrug resistance was noted in 20 patients to both rifampicin and dapsone 16 and in four patients to both ofloxacin and dapsone in Brazil, India, and Indonesia.

However, these studies highlight the need for increased vigilance to AMR. Regardless of clinical outcome, the WHO recommends that patients beginning MDT who are found to have resistance to rifampicin alone or in conjunction with dapsone should restart a course of second-line therapy [Table 2].{Table 2}

 Conclusions



We can infer that our article assessing strategies less complex than MFP and genome sequencing are promising choices for the testing of AMR in leprosy patients. Furthermore, our analysis recommends that the extent of safe cases has not essentially expanded in late many years obtained from drug resistance testing could be used to develop a point of care and also determine strategies for effective leprosy eradication and will help in the NLEP. This information of resistant cases will become an integral component of an overall public health strategy for better patient care. In addition, that information can provide monitoring of the spread of drug-resistant M. leprae. Notwithstanding, the consistent report of safe leprosy cases is a clinical and epidemiological concern because even a few cases can be important sources for disease transmission.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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