Polymerase Chain Reaction (PCR) as a Potential Point of Care Laboratory Test for Leprosy Diagnosis-A Systematic Review

Near fatal case of Lucio leprosy with Lucio phenomenon with pleomorphic features and its successful management from a non-endemic area

Lucio leprosy is a diffuse non-nodular form of lepromatous leprosy. Lucio phenomenon is a type of reactional state which occurs in untreated cases due to the bacillary invasion of endothelial cells. We hereby describe a histopathologically confirmed case of Lucio leprosy with Lucio phenomenon. The patient presented with pleomorphic clinical features and started taking antileprosy treatment and systemic steroids. After few days of admission, she developed deep ulcers exposing the fascia. She also developed cardiogenic shock secondary to septicaemia. She was managed with inotropes and broad-spectrum antibiotics. The patient was given appropriate wound care and the ulcers healed within a period of 3 months and antileprosy drugs were continued. Our patient is a de novo case of Lucio leprosy with Lucio phenomenon and pleomorphic clinical features who developed near fatal septic shock. She was managed successfully. Despite the extensive disease manifestation, all the wounds healed completely.

A recombinant chimeric antigen constructed with B-cell epitopes from Mycobacterium leprae hypothetical proteins is effective for the diagnosis of leprosy

The diagnosis if leprosy is difficult, as it requires clinical expertise and sensitive laboratory tests. In this study, we develop a serological test for leprosy by using bioinformatics tools to identify specific B-cell epitopes from Mycobacterium leprae hypothetical proteins, which were used to construct a recombinant chimeric protein, M1. The synthetic peptides were obtained and showed good reactivity to detect leprosy patients, although the M1 chimera have showed sensitivity (Se) and specificity (Sp) values higher than 90.0% to diagnose both paucibacillary (PB) and multibacillary (MB) leprosy patients, but not those developing tegumentary or visceral leishmaniasis, tuberculosis, Chagas disease, malaria, histoplasmosis and aspergillosis, in ELISA experiments. Using sera from household contacts, values for Se and Sp were 100% and 65.3%, respectively. In conclusion, our proof-of-concept study has generated data that suggest that a new recombinant protein could be developed into a diagnostic antigen for leprosy.

Multiplex PCR-based RFLP assay for early identification of prevalent Mycobacterium leprae genotypes

Mycobacterium leprae is classified into four SNP genotypes and 16 subtypes (from 1A to 4P) that exhibit phylogeographical association reported from around the world. Among them, genotypes 1D and 3I represent more than 60% of M. leprae strains. Here, we report a new method for M. leprae genotyping which identifies the genotypes 1D and 3I by combining multiplex PCR amplification and restriction fragment length polymorphism (RFLP) of a M. leprae DNA amplicons using AgeI restriction enzyme. Agarose gel electrophoresis showed a deletion of 11 bp only among 3I genotypes by electrophoresis. When this multiplex PCR reaction is subjected to AgeI digestion, successful restriction digestion shows three bands for all the genotypes except 1D where only two bands were observed due to loss of restriction site. This method gives us the advantage of 1-step identification of the two most prevalent strains of M. leprae without using specialized equipments such as the Sanger sequencing system or quantitative PCR.

Biosensor-Based Multiple Cross Displacement Amplification for the Rapid Detection of Mycobacterium leprae

Leprosy is an ancient disease caused by Mycobacterium leprae (ML) that remains a public health problem in poverty-stricken areas worldwide. Although many ML detection techniques have been used, a rapid and sensitive tool is essential for the early detection and treatment of leprosy. Herein, we developed a rapid ML detection technique by combining multiple cross displacement amplification (MCDA) with a nanoparticle-based lateral flow biosensor (LFB), termed ML-MCDA-LFB. MCDA induced a rapid isothermal reaction using specific primers targeting the RLEP gene, and the LFB enabled instant visual amplicon detection. The pure genomic DNA of ML and nucleic acids from various pathogens were employed to evaluate and optimize the ML-MCDA-LFB assay. The optimal conditions for ML-MCDA-LFB were 68 °C and 35 min, respectively. The limit of detection for pure ML genomic DNA was 150 fg per vessel, and the specificity of detection was 100% for the experimental strains. Additionally, the entire detection process could be performed within 40 min, including the isothermal amplification (35 min) and result confirmation (1-2 min). Hence, the ML-MCDA-LFB assay was shown to be a rapid, sensitive, and visual method for detecting ML and could be used as a potential tool for early clinical diagnosis and field screening of leprosy.

Highly sensitive and rapid determination of Mycobacterium leprae based on real-time multiple cross displacement amplification

BACKGROUND

Mycobacterium leprae (ML) is the pathogen that causes leprosy, which has a long history and still exists today. ML is an intracellular mycobacterium that dominantly induces leprosy by causing permanent damage to the skin, nerves, limbs and eyes as well as deformities and disabilities. Moreover, ML grows slowly and is nonculturable in vitro. Given the prevalence of leprosy, a highly sensitive and rapid method for the early diagnosis of leprosy is urgently needed.

RESULTS

In this study, we devised a novel tool for the diagnosis of leprosy by combining restriction endonuclease, real-time fluorescence analysis and multiple cross displacement amplification (E-RT-MCDA). To establish the system, primers for the target gene RLEP were designed, and the optimal conditions for E-RT-MCDA at 67 °C for 36 min were determined. Genomic DNA from ML, various pathogens and clinical samples was used to evaluate and optimize the E-RT-MCDA assay. The limit of detection (LoD) was 48.6 fg per vessel for pure ML genomic DNA, and the specificity of detection was as high as 100%. In addition, the detection process could be completed in 36 min by using a real-time monitor.

CONCLUSION

The E-RT-MCDA method devised in the current study is a reliable, sensitive and rapid technique for leprosy diagnosis and could be used as a potential tool in clinical settings.

Leprosy in an Adopted Woman Diagnosed by Molecular Tools: A Case Report from a Non-Endemic Area

Coupled with its rarity in non-endemic areas, the clinical heterogeneity of leprosy makes diagnosis very challenging. We report a diagnosis of multibacillary leprosy in a 22-year-old Indian woman, adopted at the age of 10 and living in Italy. The patient presented with painful skin lesions on the face, trunk, and lower and upper extremities, associated with dysesthesia and a motor deficit in her left leg following corticosteroid therapy interruption. Histopathology results from the skin lesions suggested leprosy, but no acid-fast bacilli were identified. Molecular biology in a center specializing in tropical diseases confirmed the diagnosis, allowing prompt and adequate treatment. Genotype analysis allowed the identification of a genotype 1D of M. leprae, facilitating the epidemiological investigation of the plausible infection origin. No resistances to rifampicin, dapsone, or ofloxacin were detected. Leprosy will continue to exist in high-income nations, and the incidence may rise over time due to increasing migration and globalization. CARE guidelines were followed.

ELISA Test Based on the Phenolic Glycolipid-I (PGL-I) of Mycobacterium leprae: A Reality of a Laboratory from a Non-Endemic Country

Background: Leprosy is a neglected tropical disease caused by Mycobacterium leprae, leading to disabilities if untreated. The ELISA based on phenolic glycolipid I (PGL-I), or its synthetic version ND-O-BSA, is almost universally positive in multibacillary leprosy and thus extensively used in endemic countries. Household contacts with a positive antibody titer have ~6-fold higher probability to develop the disease than those with a negative titer. Thus, the aim of the study was to evaluate the performance of this ELISA in the setting of a non-endemic country. Methods: We calculate the cut-off using optimized O.D. thresholds, generated by receiver operating characteristics (ROC) curve analysis, testing 39 well-characterized sera obtained from lepromatous leprosy patients with strongly positive ND-O-BSAELISA titer and 39 sera from healthy non-endemic patients never exposed to M. leprae or M. tuberculosis. Indeed, we tested a second set of sera from suspected or confirmed leprosy or household contacts (SLALT group, n=50), and patients with tuberculosis (control group, n=40). Results: We detected 56.4% of SLALT and 22.5% of tuberculosis as positive, consistent with the literature. Conclusion: The ELISA based on ND-O-BSA may thus be considered a good option to be used in a non-endemic area as a screening tool in at risk population usually coming to our center.

NDO-BSA, LID-1, and NDO-LID Antibody Responses for Infection and RLEP by Quantitative PCR as a Confirmatory Test for Early Leprosy Diagnosis

Diagnostic tests for leprosy are limited, especially to identify early leprosy cases. We performed active case findings of leprosy to validate three potential antigen candidates and one molecular target. Cases were diagnosed by characteristic skin lesions, nerve enlargement, or skin sensation loss. Serum samples obtained from all subjects were tested by ELISA to assess antibody titers to three Mycobacterium leprae specific antigens: NDO-BSA, LID-1, and NDO-LID. Most of the field cases on Mosqueiro Island, northern Brazil, also collected slit skin smear for qPCR. Active case finding diagnosed 105 new cases of leprosy out of 894 subjects (11.7%), revealing a high prevalence of M. leprae in the region. With the use of amplification of the M. leprae-specific RLEP by qPCR, 68/79 (86.07%) of these cases were positive, confirming leprosy in subjects diagnosed in the field. Patients diagnosed at the leprosy reference center showed much higher antibody titers to all three antigens, while titers of patients from the field were significantly lower. Our results support previous findings that active surveillance by experienced leprologists can diagnose additional cases based on clinical findings, that many would not be identified using ELISA assay with the available biomarkers, and that RLEP qPCR may be used to confirm the majority of the field cases.

Development and validation of a multiplex real-time qPCR assay using GMP-grade reagents for leprosy diagnosis

Leprosy is a chronic dermato-neurological disease caused by Mycobacterium leprae, an obligate intracellular bacterium. Timely detection is a challenge in leprosy diagnosis, relying on clinical examination and trained health professionals. Furthermore, adequate care and transmission control depend on early and reliable pathogen detection. Here, we describe a qPCR test for routine diagnosis of leprosy-suspected patients. The reaction simultaneously amplifies two specific Mycobacterium leprae targets (16S rRNA and RLEP), and the human 18S rRNA gene as internal control. The limit of detection was estimated to be 2.29 copies of the M. leprae genome. Analytical specificity was evaluated using a panel of 20 other skin pathogenic microorganisms and Mycobacteria, showing no cross-reactivity. Intra- and inter-operator C_p variation was evaluated using dilution curves of M. leprae DNA or a synthetic gene, and no significant difference was observed between three operators in two different laboratories. The multiplex assay was evaluated using 97 patient samples with clinical and histopathological leprosy confirmation, displaying high diagnostic sensitivity (91%) and specificity (100%). Validation tests in an independent panel of 50 samples confirmed sensitivity and specificity of 97% and 98%, respectively. Importantly, assay performance remained stable for at least five months. Our results show that the newly developed multiplex qPCR effectively and specifically detects M. leprae DNA in skin samples, contributing to an efficient diagnosis that expedites the appropriate treatment.

Leprosy is a chronic dermato-neurological disease caused by Mycobacterium leprae, an obligate intracellular bacterium. Diagnosis of leprosy often relies on skin examinations for clinical signs, bacilli staining from skin smears and invasive skin biopsies. However, the spectrum of clinical manifestations and, often, low bacilli numbers can hinder accurate diagnosis. Timely detection is a challenge in leprosy diagnosis, relying on clinical examination and requiring trained health professionals. Proper intervention for adequate care and transmission control depends on early and reliable pathogen detection. Quantitative PCR methods for detecting bacterial DNA are more sensitive and could aid in differentially diagnosing leprosy from other dermatological conditions. In this work, we present a new multiplex PCR that was assessed for quality control standards, and the data indicate that the assay is stable and reproducible. The results presented here are the basis of a novel and robust tool with potential to increase the accuracy of leprosy diagnosis in routine or reference laboratories.

Symmetrical centrofacial erythematous plaques and papules: A clinicopathological challenge

Facial papular eruptions remain a diagnostic dilemma for the dermatologist with a wide range of inflammatory and infectious conditions manifesting in this manner. Here, we present a case of a 29-year-old, otherwise healthy man from North India with asymptomatic well-defined normoaesthetic symmetrical papules and plaques over the upper and mid-face of 3 months duration. Skin biopsy showed perivascular and periappendageal well-defined collections of foamy macrophages and epithelioid cells in superficial and deep dermis, characteristic of borderline lepromatous leprosy. Though acid-fast stain for lepra bacilli was negative both on lesional biopsy specimen and lesional and ear lobe slit skin smear, a 16s ribosomal ribonucleic acid (16s-r-RNA) polymerase chain reaction on skin biopsy specimen was found to be positive for lepra bacilli. A final diagnosis of borderline lepromatous leprosy in type I reaction was made and the patient received World Health Organization (WHO) multibacillary (MB) multidrug therapy along with oral steroids. This case highlights the unusual localized involvement in a case of MB leprosy lacking all the three cardinal features of leprosy, i.e. sensory loss, peripheral nerve involvement, and acid-fast bacilli positivity on biopsy or slit skin smear but diagnosed on the basis of characteristic histology and positive polymerase chain reaction results.

RLEP LAMP for the laboratory confirmation of leprosy: towards a point-of-care test

BACKGROUND

Nucleic acid-based amplification tests (NAAT), above all (q)PCR, have been applied for the detection of Mycobacterium leprae in leprosy cases and household contacts with subclinical infection. However, their application in the field poses a range of technical challenges. Loop-mediated isothermal amplification (LAMP), as a promising point-of-care NAAT does not require sophisticated laboratory equipment, is easy to perform, and is applicable for decentralized diagnosis at the primary health care level. Among a range of gene targets, the M. leprae specific repetitive element RLEP is regarded as highly sensitive and specific for diagnostic applications.  METHODS: Our group developed and validated a dry-reagent-based (DRB) RLEP LAMP, provided product specifications for customization of a ready-to-use kit (intended for commercial production) and compared it against the in-house prototype. The assays were optimized for application on a Genie® III portable fluorometer. For technical validation, 40 "must not detect RLEP" samples derived from RLEP qPCR negative exposed and non-exposed individuals, as well as from patients with other conditions and a set of closely related mycobacterial cultures, were tested together with 25 "must detect RLEP" samples derived from qPCR confirmed leprosy patients. For clinical validation, 150 RLEP qPCR tested samples were analyzed, consisting of the following categories: high-positive samples of multibacillary (MB) leprosy patients (> 10.000 bacilli/extract), medium-positive samples of MB leprosy patients (1.001-10.000 bacilli/extract), low-positive samples of MB leprosy patients (1-1.000 bacilli/extract), endemic controls and healthy non-exposed controls; each n = 30.  RESULTS: Technical validation: both LAMP formats had a limit of detection of 1.000 RLEP copies, i.e. 43-27 bacilli, a sensitivity of 92% (in-house protocol)/100% (ready-to-use protocol) and a specificity of 100%. Reagents were stable for at least 1 year at 22 °C. Clinical validation: Both formats showed a negativity rate of 100% and a positivity rate of 100% for high-positive samples and 93-100% for medium positive samples, together with a positive predictive value of 100% and semi-quantitative results. The positivity rate for low-positive samples was 77% (in-house protocol)/43% (ready-to-use protocol) and differed significantly between both formats.  CONCLUSIONS: The ready-to-use RLEP DRB LAMP assay constitutes an ASSURED test ready for field-based evaluation trials aiming for routine diagnosis of leprosy at the primary health care level.

Diagnostic utility of PCR in detection of clinical cases and carriers of leprosy: A cross sectional study at a tertiary care teaching hospital in central India

PURPOSE

Since ancient era leprosy is existing across the world. India, Indonesia and Brazil still harbour major proportion of global cases. Child leprosy and Grade II disability indicate delayed diagnosis and persistence of transmission in community. So, this study was conducted with aim to evaluate the diagnostic efficacy of PCR in comparison to SSS (Slit Skin Smear) microscopy for detection of leprosy in early stages in both cases and carriers (contacts).

METHODS

A cross sectional observational study was conducted on 100 subjects including 50 clinically diagnosed new cases of leprosy and their 50 contacts. Each group was subjected to SSS (Slit Skin Smear) microscopy and PCR using RLEP gene as target.

RESULTS

The overall male: female ratio was 2.44. The Slit Skin smear (SSS) microscopy positivity was 34% (n = 17/50) among cases while it was 0% (n = 0/50) among contacts. The overall positivity for PCR was 42% (n = 42/100) being 66% (n = 33/50) in cases and 18% (n = 9/50) in contacts. About 30% (n = 25/83) of all the microscopically negative subjects were found to be positive by PCR.

CONCLUSIONS

PCR was found to be a better diagnostic tool both among cases and their contacts. It should be used for screening contacts for early diagnosis and treatment and thus preventing transmission in community.

KEY MESSAGE

To diagnose case and contacts of leprosy in early stages even in very low bacterial density using PCR.

Leprosy incidence and risk estimates in a 33-year contact cohort of leprosy patients

Reduction in incidence has been associated with the introduction of novel approaches, like chemo/immune-prophylaxis. Incidence determined through follow-up cohort studies can evaluate the implementation of these innovative policies towards control and prevention. We have assessed the incidence in our contacts cohort over past 33 years, considering the effect of demographic and clinical variables. Survival analysis was used to estimate the risk of leprosy. A total of 9024 contacts were evaluated, of which 192 developed leprosy, resulting in an overall incidence of 1.4/1000 person-years. The multivariate analysis showed that the major risk factors were (i) contact from MB index cases and (ii) consanguinity (iii) intra household contact. Lower risk was detected for contacts with BCG scar who were revaccinated. There was a significant decrease in accumulated risk between the 2011-2019 period compared with 1987, probably linked to the improvement in laboratory tools to monitor contacts, thereby providing early diagnosis of contacts at intake and reduction of transmission. Our findings suggest that a combination of contact surveillance and tracing, adequate neurodermatological examination, and availability of molecular tools is highly effective in supporting early diagnosis, while a second dose of the BCG vaccination can exert extra protection.

Novel Diagnostics for Kaposi Sarcoma and Other Skin Diseases in Resource-Limited Settings

In resource-limited settings, point-of-care diagnostic devices have the potential to reduce diagnostic delays and improve epidemiologic surveillance of dermatologic conditions. We outline novel-point-of care diagnostics that have recently been developed for dermatologic conditions that primarily affect patients living in resource-limited settings, namely, Kaposi sarcoma, cutaneous leishmaniasis, leprosy, Buruli ulcer, yaws, onchocerciasis, and lymphatic filariasis. All of the technologies described in this article are prototypes, and some have undergone field testing. These devices still require validation in real-world settings and effective pricing to have a major impact on dermatologic care in resource-limited settings.

Serological and molecular detection of infection with Mycobacterium leprae in Brazilian six banded armadillos (Euphractus sexcinctus)

Leprosy was recognized as a zoonotic disease, associated with nine-banded armadillos (Dasypus novemcinctus) in the Southern United States of America in 2011. In addition, there is growing evidence to support a role for armadillos in zoonotic leprosy in South America. The current study evaluated twenty specimens of the six-banded armadillo (Euphractus sexcinctus), collected from rural locations in the state of Rio Grande do Norte (RN), Brazil for evidence of infection with Mycobacterium leprae. Serum was examined using two "in-house" enzyme-linked immunosorbent assays (ELISAs) and via two commercially available (ML flow and NDO-LID®) immunochromatographic lateral flow (LF) tests, for detection of the PGL-I and/or LID-1 antigens of the bacterium. The presence of M. leprae DNA in liver tissue was examined using the multi-copy, M. leprae-specific repetitive element (RLEP), as target in conventional and nested PCR assays. Molecular and anti-PGL-I-ELISA data indicated that 20/20 (100 %) of the armadillos were infected with M. leprae. The corresponding detection levels recorded with the LF tests were 17/20 (85 %) and 16/20 (85 %), for the NDO-LID® and ML flow tests, respectively. Our results indicate that, in common with D. novemcinctus, six banded armadillos (a species hunted and reared as a food-source in some regions of Brazil, including RN), represent a potential reservoir of M. leprae and as such, their role in a possible zoonotic cycle of leprosy within Brazil warrants further investigation.

Develop and Field Evolution of Single Tube Nested PCR, SYBRGreen PCR Methods, for the Diagnosis of Leprosy in Paraffin-embedded Formalin Fixed Tissues in Yunnan Province, a Hyper endemic Area of Leprosy in China

BACKGROUND

Detection and pathology analysis of Mycobacterium leprae using skin biopsy tissues are essential for leprosy diagnosis and monitoring response to treatment. Although formalin fixation of patient tissues may not be ideal for molecular studies, biopsy samples are the most accessible material from suspected cases. Therefore, clinical molecular laboratories must be able to utilize formalin-fixed, paraffin-embedded (FFPE) material.

OBJECTIVE

To determine the best molecular method for diagnosing and monitoring leprosy in FFPE specimens, we developed a single-tube nested PCR (STNPCR) (131 bp) and SYBRGreen PCR (101 bp) assay using primers for the M. leprae-specific repetitive element (RLEP) gene and evaluated the results compared to those using previously established RLEP primers (372 bp).

METHODS

FFPE biopsy samples obtained from 145 leprosy patients (during or after multidrug therapy (MDT)) and patients with 29 other confounding dermatoses were examined by the bacteria index (BI) and by simple PCR, STNPCR, and SYBRGreen PCR using primers amplifying a 372-bp, 131-bp or 101-bp fragment of RLEP, respectively.

RESULTS

In leprosy patients receiving MDT, STNPCR showed a highest specificity of 100% and a positive predictive value (PPV) of 100%. For multibacillary (MB), paucibacillary (PB) and all leprosy patients, the highest sensitivities were 91.42%, 39.13%, and 67.92%, negative predictive values (NPVs) were 8.57%, 60.36%, and 32.07%, and the highest accuracies were 93.93%, 62.67%, and 74.81%, respectively, higher than the results of SYBRGreen PCR and simple PCR. For post-MDT leprosy patients, SYBRGreen PCR showed the highest sensitivity of 50.0%, highest specificity of 100%, a PPV of 100%, an NPV of 100% and the highest accuracy of 83.72% for MB patients, which were higher than those of STNPCR and simple PCR. STNPCR showed the highest sensitivity of 26.66% and 34.48%, highest specificity of 100% and 100%, a PPV of 100% and 100%, NPV of 72.50% and 60.21%, and highest accuracy of 75.00% and 67.24% for PB and leprosy patients, respectively, higher than those of SYBRGreen PCR and simple PCR.

CONCLUSIONS

These findings suggest that STNPCR or SYBRGreen PCR (131-bp and 101-bp fragment amplification, respectively) for RLEP using FFPE specimens performs better as a diagnostic test and for monitoring response to MDT than does simple PCR based on 372-bp fragment amplification. Additionally, STNPCR showed increased sensitivity for PB diagnosis using FFPE specimens, which can be transferred remotely or retrieved from previous leprosy patients.

Development and evaluation of a droplet digital PCR assay for the diagnosis of paucibacillary leprosy in skin biopsy specimens

BACKGROUND

The reduced amounts of Mycobacterium leprae (M. leprae) among paucibacillary (PB) patients reflect the need to further optimize methods for leprosy diagnosis. An increasing number of reports have shown that droplet digital polymerase chain reaction (ddPCR) is a promising tool for diagnosis of infectious disease among samples with low copy number. To date, no publications have investigated the utility of ddPCR in the detection of M. leprae. The aim of this study was to develop and evaluate a ddPCR assay for the diagnosis of PB leprosy.

METHODOLOGY

The two most sensitive DNA targets for detection of M. leprae were selected from electronic databases for assessment of sensitivity and specificity by quantitative polymerase chain reaction (qPCR) and ddPCR. Control patients (n = 59) suffering from other dermatological diseases were used to define the cut-off of the duplex ddPCR assay. For comparative evaluation, qPCR and ddPCR assays were performed in 44 PB patients and 68 multibacillary (MB) patients.

PRINCIPAL FINDINGS

M. leprae-specific repetitive element (RLEP) and groEL (encoding the 65 kDa molecular chaperone GroEL) were used to develop the ddPCR assay by systematically analyzing specificity and sensitivity. Based on the defined cut-off value, the ddPCR assay showed greater sensitivity in detecting M. leprae DNA in PB patients compared with qPCR (79.5% vs 36.4%), while both assays have a 100% sensitivity in MB patients.

CONCLUSIONS/SIGNIFICANCE

We developed and evaluated a duplex ddPCR assay for leprosy diagnosis in skin biopsy samples from leprosy patients. While still costly, ddPCR might be a promising diagnostic tool for detection of PB leprosy.