A simplified reverse transcriptase PCR for rapid detection ofMycobacterium lepraein skin specimens

Comparative analysis of the leprosy detection rate regarding its clinical spectrum through PCR using the 16S rRNA gene: a scientometrics and meta-analysis

Background

Leprosy is a chronic and disabling infectious disease caused by Mycobacterium leprae. It has a wide clinical spectrum and is operationally classified into paucibacillary (PB) and multibacillary (MB) cases. There is evidence that the 16S rRNA gene can be used in Polymerase Chain Reaction (PCR) for complementary detection with high sensitivity and specificity. However, there is no literature convention on its diagnostic correspondence regarding the particular operational classification of the disease. This study aimed to correlate, through a meta-analysis, the detection rate of leprosy between the PCR method with the 16S rRNA gene in the clinical forms PB and MB in relation to confirmed cases.

Methods

This is a systematic review and meta-analysis study conducted according to the PRISMA 2020 guidelines, using the search descriptors with "AND": "Leprosy"; "Polymerase Chain Reaction"; "16S rRNA" in the PUBMED, SciELO, LILACS, and Science Direct databases. The search was limited to original observational articles in Portuguese, English, or Spanish, with no defined time frame. The methodological quality assessment of the selected articles was performed using the JBI checklists. A scientometric approach to the article using used the VOS Viewer and Scimago Graphica software. The meta-analysis was conducted using Comprehensive Meta-Analyses software, under Pearson's Correlation effect test and fixed effect model and subgroup analysis concerning the type of sample analyzed.

Results

The study was significant from the perspective of the paucibacillary group (Clinical biopsy: -0.45 [95% CI= -0.63 - -0.22], p < 0.001/ Slit smear skin: -0.52 [95% CI= -0.65 - -0.36], p < 0.001 / Overall: -0.50 [95% CI= -0.61 - -0.37], p < 0.001). The PCR diagnostic method for the16S rRNAgene ofM. lepraehas low viability and diagnostic sensitivity in both clinical biopsy samples and leprosy skin smears.

Conclusion

This implies little validation of it as a PCR target gene for diagnosing the disease, highlighting limitations in the actual technique.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42024588790.

Human Skin as an Ex Vivo Model for Maintaining Mycobacterium leprae and Leprosy Studies

The in vitro cultivation of M. leprae has not been possible since it was described as causing leprosy, and the limitation of animal models for clinical aspects makes studies on leprosy and bacteria-human host interaction a challenge. Our aim was to standardize the ex vivo skin model (hOSEC) to maintenance and study of M. leprae as an alternative animal model. Bacillary suspensions were inoculated into human skin explants and sustained in DMEM medium for 60 days. Explants were evaluated by RT-PCR-16SrRNA and cytokine gene expression. The viability and infectivity of bacilli recovered from explants (D28 and D60) were evaluated using the Shepard's model. All explants were RT-PCR-16SrRNA positive. The viability and infectivity of recovered bacilli from explants, analyzed after 5 months of inoculation in mice, showed an average positivity of 31%, with the highest positivity in the D28 groups (80%). Furthermore, our work showed different patterns in cytokine gene expression (TGF-β, IL-10, IL-8, and TNF-α) in the presence of alive or dead bacilli. Although changes can be made to improve future experiments, our results have demonstrated that it is possible to use the hOSEC to maintain M. leprae for 60 days, interacting with the host system, an important step in the development of experimental models for studies on the biology of the bacillus, its interactions, and drug susceptibility.

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.

Diagnostic accuracy of tests for leprosy: a systematic review and meta-analysis

OBJECTIVES

Owing to difficulties in the clinical diagnosis of leprosy, several complementary tests have been developed and used. The aim was to systematically summarize the accuracy of diagnostic tests for leprosy.

METHODS

We searched for relevant articles in Embase, Medline, and Global Health databases, until June 2017. Studies evaluating the accuracy of any diagnostic techniques for differentiating between people with and without leprosy were included. Studies solely focusing on differentiating between the separate forms of leprosy were excluded. Our protocol was registered on PROSPERO (CRD42017071803). We assessed study quality using the QUADAS-2 checklist. A bivariate random effects regression model was used for the meta-analyses.

RESULTS

We included 78 studies, most of those evaluating the detection of IgM antibodies against phenolic glycolipid I using ELISA. Sensitivity of the 39 studies evaluating ELISA was 63.8% (95% CI 55.0-71.8); specificity 91.0% (95% CI 86.9-93.9). The lateral flow test (nine studies) and the agglutination test (five studies) had a slightly higher sensitivity and a slightly lower specificity. Sensitivity of qPCR was (five studies) 78.5% (95% CI 61.9-89.2) and specificity 89.3% (95% CI 61.4-97.8). Sensitivity of conventional PCR was (17 studies) 75.3% (95% CI 67.9-81.5) and specificity 94.5% (95% CI 91.4-96.5).

CONCLUSIONS

Although the test accuracy looks reasonable, the studies suffered from heterogeneity and low methodological quality.

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

Leprosy is an infectious disease caused by Mycobacterium leprae and mainly affects skin, peripheral nerves, and eyes. Suitable tools for providing bacteriological evidence of leprosy are needed for early case detection and appropriate therapeutic management. Ideally these tools are applicable at all health care levels for the effective control of leprosy. This paper presents a systematic review analysis in order to investigate the performance of polymerase chain reaction (PCR) vis-à-vis slit skin smears (SSS) in various clinical settings and its potential usefulness as a routine lab test for leprosy diagnosis. Records of published journal articles were identified through PubMed database search. Twenty-seven articles were included for the analysis. The evidence from this review analysis suggests that PCR on skin biopsy is the ideal diagnostic test. Nevertheless, PCR on SSS samples also seems to be useful with its practical value for application, even at primary care levels. The review findings also indicated the necessity for improving the sensitivity of PCR and further research on specificity in ruling out other clinical conditions that may mimic leprosy. The M. leprae-specific repetitive element (RLEP) was the most frequently-used marker although its variable performance across the clinical sites and samples are a matter of concern. Undertaking further research studies with large sample numbers and uniform protocols studied simultaneously across multiple clinical sites is recommended to address these issues.

qPCR detection of Mycobacterium leprae in biopsies and slit skin smear of different leprosy clinical forms

Leprosy, whose etiological agent is Mycobacterium leprae, is a chronic infectious disease that mainly affects the skin and peripheral nervous system. The diagnosis of leprosy is based on clinical evaluation, whereas histopathological analysis and bacilloscopy are complementary diagnostic tools. Quantitative PCR (qPCR), a current useful tool for diagnosis of infectious diseases, has been used to detect several pathogens including Mycobacterium leprae. The validation of this technique in a robust set of samples comprising the different clinical forms of leprosy is still necessary. Thus, in this study samples from 126 skin biopsies (collected from patients on all clinical forms and reactional states of leprosy) and 25 slit skin smear of leprosy patients were comparatively analyzed by qPCR (performed with primers for the RLEP region of M. leprae DNA) and routine bacilloscopy performed in histological sections or in slit skin smear. Considering clinical diagnostic as the gold standard, 84.9% of the leprosy patients were qPCR positive in skin biopsies, resulting in 84.92% sensitivity, with 84.92 and 61.22% positive (PPV) and negative (NPV) predictive values, respectively. Concerning bacilloscopy of histological sections (BI/H), the sensitivity was 80.15% and the PPV and NPV were 80.15 and 44.44%, respectively. The concordance between qPCR and BI/H was 87.30%. Regarding the slit skin smear, 84% of the samples tested positive in the qPCR. Additionally, qPCR showed 100% specificity, since all samples from different mycobacteria, from healthy individuals, and from other granulomatous diseases presented negative results. In conclusion, the qPCR technique for detection of M. leprae using RLEP primers proved to be specific and sensitive, and qPCR can be used as a complementary test to diagnose leprosy irrespective of the clinical form of disease.

Critical analysis: use of polymerase chain reaction to diagnose leprosy

ABSTRACT Leprosy is a neglected tropical disease and an important public health problem, especially in developing countries. It is a chronic infectious disease that is caused by Mycobacterium leprae, which has a predilection for the skin and peripheral nerves. Although it has low sensitivity, slit-skin smear (SSS) remains the conventional auxiliary laboratory technique for the clinical diagnosis of leprosy. Polymerase chain reaction (PCR) is a molecular biology technique that holds promise as a simple and sensitive diagnostic tool. In the present study, the performance of two PCR methods, using different targets, PCR-LP and PCR-P, were compared with SSS with regard to leprosy diagnosis in a reference laboratory. M. leprae DNA was extracted from 106 lymph samples of 40 patients who had clinical suspicion of leprosy. The samples were subjected to both PCR techniques and SSS. Amplification of the human b-globin gene was used as PCR inhibitor control. The specificity of both PCR techniques was 100%, and sensitivity was 0.007 and 0.015 µg/ml for PCR-LP and PCR-P, respectively. No significant difference was found between either the PCR-LP or PCR-P results and SSS results (p > 0.05). Although PCR is not yet a replacement for SSS in the diagnosis of leprosy, this technique may be used as an efficient auxiliary tool for early detection of the disease, especially in endemic regions. This strategy may also be useful in cases in which SSS results are negative (e.g., in paucibacillary patients) and cases in which skin biopsy cannot be performed.

Leprosy: a review of laboratory and therapeutic aspects--part 2

Leprosy is a chronic infectious condition caused by Mycobacterium leprae(M. leprae). It is endemic in many regions of the world and a public health problem in Brazil. Additionally, it presents a wide spectrum of clinical manifestations, which are dependent on the interaction between M. leprae and host, and are related to the degree of immunity to the bacillus. The diagnosis of this disease is a clinical one. However, in some situations laboratory exams are necessary to confirm the diagnosis of leprosy or classify its clinical form. This article aims to update dermatologists on leprosy, through a review of complementary laboratory techniques that can be employed for the diagnosis of leprosy, including Mitsuda intradermal reaction, skin smear microscopy, histopathology, serology, immunohistochemistry, polymerase chain reaction, imaging tests, electromyography, and blood tests. It also aims to explain standard multidrug therapy regimens, the treatment of reactions and resistant cases, immunotherapy with bacillus Calmette-Guérin (BCG) vaccine and chemoprophylaxis.

Evaluation of major membrane protein-I as a serodiagnostic tool of pauci-bacillary leprosy

We have previously shown that the serodiagnosis using major membrane protein-II (MMP-II) is quite efficient in diagnosing leprosy. However, the detection rate of pauci-bacillary (PB) leprosy patients is still low. In this study, we examined the usefulness of major membrane protein-I (MMP-I) from Mycobacterium leprae. The MMP-I-based serodiagnosis did not show significantly high detection rate. However, when the mixture of MMP-I and MMP-II antigens was used, we detected 94.4% of multi-bacillary leprosy and 39.7% of PB patients. There were little correlation between the titers of anti-MMP-I antibodies (Abs) and that of anti-MMP-II Abs in PB patients' sera. Ten out of 46 MMP-II-negative PB leprosy patients were MMP-I positive, so that the detection rate of PB leprosy patient increased from 39.7% to 53.8% by taking either test positive strategy. We concluded that MMP-I can complement the MMP-II-based serodiagnosis of leprosy.

PCR-based techniques for leprosy diagnosis: from the laboratory to the clinic

In leprosy, classic diagnostic tools based on bacillary counts and histopathology have been facing hurdles, especially in distinguishing latent infection from active disease and diagnosing paucibacillary clinical forms. Serological tests and IFN-gamma releasing assays (IGRA) that employ humoral and cellular immune parameters, respectively, are also being used, but recent results indicate that quantitative PCR (qPCR) is a key technique due to its higher sensitivity and specificity. In fact, advances concerning the structure and function of the Mycobacterium leprae genome led to the development of specific PCR-based gene amplification assays for leprosy diagnosis and monitoring of household contacts. Also, based on the validation of point-of-care technologies for M. tuberculosis DNA detection, it is clear that the same advantages of rapid DNA detection could be observed in respect to leprosy. So far, PCR has proven useful in the determination of transmission routes, M. leprae viability, and drug resistance in leprosy. However, PCR has been ascertained to be especially valuable in diagnosing difficult cases like pure neural leprosy (PNL), paucibacillary (PB), and patients with atypical clinical presentation and histopathological features compatible with leprosy. Also, the detection of M. leprae DNA in different samples of the household contacts of leprosy patients is very promising. Although a positive PCR result is not sufficient to establish a causal relationship with disease outcome, quantitation provided by qPCR is clearly capable of indicating increased risk of developing the disease and could alert clinicians to follow these contacts more closely or even define rules for chemoprophylaxis.

Comparison between microsatellites and Ml MntH gene as targets to identify Mycobacterium leprae by PCR in leprosy

BACKGROUND

The Polymerase Chain Reaction (PCR) technique has been frequently used in the molecular diagnosis of leprosy.

OBJECTIVES

To compare the results of PCR with four pairs of Mycobacterium leprae specific primers as well as to compare these results to multibacillary (MB) and paucibacillary (PB) leprosy according to the WHO operational classification.

METHOD

28 DNA samples, collected from the frozen skin biopsies and biopsy imprints on filter paper of 23 patients (14 MB and PB 9), were examined for PCR using primers which amplify 131, 151 and 168bp of specific microsatellite regions and a 336 fragment of the Ml MntH (ML2098) gene.

RESULTS

M.leprae bacillus could be detected in 22 (78.6%) of the 28 samples. 9 (45%) of the 20 biopsy samples and 6 (75%) of the 8 imprints were positive to TTC. 7 (35.5%) skin biopsy specimens and 5 (62.5%) imprints were positive to AGT, and 11 (55%) biopsies and 4 (50%) were positive to AGT. 11 (55%) skin biopsies and 4 (50%) imprints were positive to AT. 8(38%) skin biopsies and 5 (62.5%) imprints were positive to the Ml MntH gene. In the MB group, the microsatellites detected the bacillus in 78.5% of the samples, and the Ml MntH gene in 57.1% of the samples, independent of the clinical material. In the PB group 55.5% of samples were positive to the microsatellite primers, while 22.2% were positive to the Ml MntH gene.

CONCLUSIONS

These results show that both the specific regions of microsatellites, as well as the Ml MntH gene fragment can be useful tools for detecting the M. leprae DNA by PCR in frozen skin biopsy samples and filter paper biopsy imprints.

Use of the polymerase chain reaction to detect Mycobacterium leprae in urine

Leprosy is an infectious disease caused by Mycobacterium leprae. The polymerase chain reaction (PCR) has been applied to detect M. leprae in different clinical samples and urine seems to be attractive for this purpose. PCR was used to improve the sensitivity for diagnosing leprosy by amplifying a 151-bp PCR fragment of the M. leprae pra gene (PCR-Pra) in urine samples. Seventy-three leprosy patients (39 males and 34 females, 14 to 78 years old) were selected for leprosy diagnosis at a reference laboratory in Maringá, PR, Brazil. Of these, 36 were under anti-leprosy multidrug therapy with dapsone and rifampicin for tuberculoid (TT) and dapsone, rifampicin and clofazimine for borderline (BB) and lepromatous (LL) forms. The control group contained 50 healthy individuals without any clinical history of leprosy. DNA isolated from leprosy patients' urine samples was successfully amplified by PCR-Pra in 46.6% (34/73) of the cases. The positivity of PCR-Pra for patients with the TT form was 75% for both patients under treatment and non-treated patients (P = 0.1306). In patients with the LL form, PCR-Pra positivity was 52 and 30% for patients under treatment and non-treated patients, respectively (P = 0.2386). PCR-Pra showed a statistically significant difference in detecting M. leprae between the TT and LL forms of leprosy in patients under treatment (P = 0.0033). Although the current study showed that the proposed PCR-Pra has some limitations in the detection of M. leprae, this method has the potential to be a useful tool for leprosy diagnosis mainly in TT leprosy where the AFB slit-skin smear is always negative.

Dynamics of Mycobacterium leprae transmission in environmental context: deciphering the role of environment as a potential reservoir

Leprosy is a disease caused by Mycobacterium leprae. Various modes of transmission have been suggested for this disease. Transmission and risk of the infection is perhaps related to presence of the infectious cases and is controlled by environmental factors. Evidence suggests that humidity may favor survival of M. leprae in the environment. Several reports show that non-human sources like 'naturally' infected armadillos or monkeys could act as reservoir for M. leprae. Inanimate objects or fomites like articles used by infectious patients may theoretically spread infection. However, it is only through detailed knowledge of the biodiversity and ecology that the importance of this mode of transmission can be fully assessed. Our study focuses here to decipher the role of environment in the transmission of the disease. Two hundred and seven soil samples were collected from a village in endemic area where active cases also resided at the time of sample collection. Slit skin smears were collected from 13 multibacillary (MB) leprosy patients and 12 household contacts of the patients suspected to be hidden cases. DNA and RNA of M. leprae were extracted and amplified using M. leprae specific primers. Seventy-one soil samples showed presence of M. leprae DNA whereas 16S rRNA could be detected in twenty-eight of these samples. Samples, both from the environment and the patients, exhibited the same genotype when tested by single nucleotide polymorphism (SNP) typing. Genotype of M. leprae found in the soil and the patients residing in the same area could help in understanding the transmission link in leprosy.

Evaluation of qPCR-based assays for leprosy diagnosis directly in clinical specimens

The increased reliability and efficiency of the quantitative polymerase chain reaction (qPCR) makes it a promising tool for performing large-scale screening for infectious disease among high-risk individuals. To date, no study has evaluated the specificity and sensitivity of different qPCR assays for leprosy diagnosis using a range of clinical samples that could bias molecular results such as difficult-to-diagnose cases. In this study, qPCR assays amplifying different M. leprae gene targets, sodA, 16S rRNA, RLEP and Ag 85B were compared for leprosy differential diagnosis. qPCR assays were performed on frozen skin biopsy samples from a total of 62 patients: 21 untreated multibacillary (MB), 26 untreated paucibacillary (PB) leprosy patients, as well as 10 patients suffering from other dermatological diseases and 5 healthy donors. To develop standardized protocols and to overcome the bias resulted from using chromosome count cutoffs arbitrarily defined for different assays, decision tree classifiers were used to estimate optimum cutoffs and to evaluate the assays. As a result, we found a decreasing sensitivity for Ag 85B (66.1%), 16S rRNA (62.9%), and sodA (59.7%) optimized assay classifiers, but with similar maximum specificity for leprosy diagnosis. Conversely, the RLEP assay showed to be the most sensitive (87.1%). Moreover, RLEP assay was positive for 3 samples of patients originally not diagnosed as having leprosy, but these patients developed leprosy 5-10 years after the collection of the biopsy. In addition, 4 other samples of patients clinically classified as non-leprosy presented detectable chromosome counts in their samples by the RLEP assay suggesting that those patients either had leprosy that was misdiagnosed or a subclinical state of leprosy. Overall, these results are encouraging and suggest that RLEP assay could be useful as a sensitive diagnostic test to detect M. leprae infection before major clinical manifestations.

Laboratory diagnosis of Buruli ulcer disease

Buruli ulcer disease (BUD), caused by Mycobacterium ulcerans, has become the third most common mycobacterial disease worldwide. Antimycobacterial therapy is considered the treatment of choice. With the introduction of antimycobacterial treatment, laboratory confirmation of clinically suspected cases became crucial for the clinical management of BUD. Currently available diagnostic laboratory tests include microscopy, culture, histopathology and IS2404 PCR. Several IS2404 PCR assays were applied for case confirmation in endemic countries, and IS2404 PCR is considered the most sensitive method for the laboratory confirmation of BUD. Due to the extended presence of mycobacterial DNA under antimycobacterial treatment, however, PCR is not suitable for monitoring of treatment success. Currently, cultures are considered the only valid confirmatory test for the detection of viable bacilli.

Challenges in the post genomic era for the development of tests for leprosy diagnosis

Leprosy diagnosis is based mainly on clinical manifestations and no laboratory test is available to diagnose asymptomatic disease or to predict disease progression among exposed individuals. Novel comparative genomic in silico analyses and molecular biology tools have discovered unique Mycobacterium leprae proteins with potential diagnostic application. Tuberculoid paucibacillary leprosy (PB) shows low antibodies titers and strong Th1 type/ IFN-gamma specific cell mediated immunity (CMI), while lepromatous multibacillary patients (MB) show high antibody titers and low CMI. Therefore, laboratory tests for PB and MB leprosy diagnosis will require CMI and antibody based assays. Serologically reactive recombinant Mycobacterium leprae proteins were identified and may be used in conjunction with PGL-I to improve MB patient diagnosis. Mycobacterium leprae recombinant proteins and synthetic peptides have been tested for CMI-interferon gamma based assays for PB diagnosis. Modified PGL-I serology incorporating new Mycobacterium leprae antigens and CMI tests based on IFN-gamma gamma production may permit the detection of leprosy PB and MB forms in endemic countries.

Molecular determination of Mycobacterium leprae viability by use of real-time PCR

Mycobacterium leprae, the etiological agent of leprosy, is noncultivable on axenic media. Therefore, the viability of M. leprae for clinical or experimental applications is often unknown. To provide new tools for M. leprae viability determination, two quantitative reverse transcriptase PCR (RT-PCR) assays were developed and characterized. M. leprae sodA mRNA and 16S rRNA were used as RNA targets, and M. leprae repetitive element (RLEP) DNA was used to determine relative bacterial numbers in the same purified bacterial preparations or from crude biological specimens. Results demonstrated that both assays were good predictors of M. leprae viability during short-term experiments (48 h) involving rifampin (rifampicin) treatment in axenic medium, within rifampin-treated murine macrophages (MPhi), or within immune-activated MPhi. Moreover, these results strongly correlated those of other M. leprae viability assays, including radiorespirometry-based and Live/Dead BacLight viability assays. The 16S rRNA/RLEP assay consistently identified the presence of M. leprae in eight multibacillary leprosy patient biopsy specimens prior to multidrug therapy (MDT) and demonstrated a decline in viability during the course of MDT. In contrast, the sodA/RLEP assay was able to detect the presence of M. leprae in only 25% of pretreatment biopsy specimens. In conclusion, new tools for M. leprae viability determination were developed. The 16S rRNA/RLEP RT-PCR M. leprae viability assay should be useful both for short-term experimental purposes and for predicting M. leprae viability in biopsy specimens to monitor treatment efficacy, whereas the sodA/RLEP RT-PCR M. leprae viability assay should be limited to short-term experimental research purposes.

Serological diagnosis of leprosy in patients in vietnam by enzyme-linked immunosorbent assay with Mycobacterium leprae-derived major membrane protein II

A serological diagnostic test using phenolic glycolipid-I (PGL-I) developed in the 1980s is commercially available, but the method is still inefficient in detecting all forms of leprosy. Therefore, more-specific and -reliable serological methods have been sought. We have characterized major membrane protein II (MMP-II) as a candidate protein for a new serological antigen. In this study, we evaluated the effectiveness of the enzyme-linked immunosorbent assay (ELISA) using the MMP-II antigen (MMP-II ELISA) for detecting antibodies in leprosy patients and patients' contacts in the mid-region of Vietnam and compared to the results to those for the PGL-I method (PGL-I ELISA). The results showed that 85% of multibacillary patients and 48% of paucibacillary patients were positive by MMP-II ELISA. Comparison between the serological tests showed that positivity rates for leprosy patients were higher with MMP-II ELISA than with PGL-I ELISA. Household contacts (HHCs) showed low positivity rates, but medical staff members showed comparatively high positivity rates, with MMP-II ELISA. Furthermore, monitoring of results for leprosy patients and HHCs showed that MMP-II is a better index marker than PGL-I. Overall, the epidemiological study conducted in Vietnam suggests that serological testing with MMP-II would be beneficial in detecting leprosy.

LightCycler real-time PCR for rapid detection and quantitation of Mycobacterium leprae in skin specimens

Diagnosis of leprosy is usually based on clinical features and skin smear results including the number of skin lesions. Mycobacterium leprae is not cultivable and bacterial enumeration by microscopic examination is required for leprosy classification, choice in choosing and monitoring chemotherapy regimens, and diagnosis of relapse. However, detection and quantification using standard microscopy yields results of limited specificity and sensitivity. We describe an extremely sensitive and specific assay for the detection and quantification of M. leprae in skin biopsy specimens. Primers that amplified a specific 171-bp fragment of M. leprae 16S rRNA gene were chosen and specificity was verified by amplicon melting temperature. The method is sensitive enough to detect as low as 20 fg of M. leprae DNA, equivalent to four bacilli. The assay showed 100% concordance with clinical diagnosis in cases of multibacillary patients, and 50% of paucibacillary leprosy. The entire procedure of DNA extraction and PCR could be performed in c. 3 h. According to normalized quantitative real-time PCR, the patients in this study had bacilli numbers in the range of 1.07 x 10(2) -1.65 x 10(8) per 6-mm3 skin biopsy specimen. This simple real-time PCR assay is a facile tool with possible applications for rapid detection and simultaneous quantification of leprosy bacilli in clinical samples.

Detection of viable Mycobacterium leprae in soil samples: insights into possible sources of transmission of leprosy

Leprosy has ceased to be a public health problem world wide, after the successful implementation of effective chemotherapy (MDT) and use of control measures. However, new cases of leprosy continue to occur. Mycobacterium leprae cannot be grown in any acceptable culture medium and besides the wild armadillos, there is no known animal reservoir for leprosy. The transmission of leprosy is believed to be due to a large extent by droplet discharge of bacilli through nose and mouth and to a lesser extent by direct contact of susceptible host with a patient for long duration. The exact role of the environment in the transmission dynamics is still speculative. In the present study, we have tried to detect viable M. leprae from soil samples in endemic areas by using molecular methods. Eighty soil samples were collected from villages of this area, DNA and RNA of M. leprae extracted and identified using specific M. leprae primers. PCR amplification was done and real-time RT-PCR was used to detect viable M. leprae. DNA targeting the 16S region of M. leprae was detected in 37.5%, whereas M. leprae RNA targeting the same region was detected in 35% of these samples. Of the total 80 samples, 40 were collected from residential areas of leprosy patients whereas 40 samples were from no-patient areas. Fifty-five percent positivity for 16S rRNA of M. leprae was observed from the "patient" area in comparison to 15% positivity from the "no-patient" area (p < 0.001). This study thus provides valuable information of presence of viable M. leprae in soil specimens, which would be of use in investigating the transmission dynamics in leprosy.

Biologia molecular aplicada às dermatoses tropicais

São apresentados conceitos básicos sobre célula, código genético e síntese protéica, e sobre algumas técnicas de biologia molecular, tais como PCR, PCR-RFLP, seqüenciamento de DNA, RT-PCR e immunoblotting. São fornecidos protocolos de extração de nucleotídeos e de proteínas, como salting out no sangue periférico e métodos do fenol-clorofórmio e do trizol em tecidos. Seguem-se exemplos comentados da aplicação de técnicas de biologia molecular para o diagnóstico etiológico e pesquisa em dermatoses tropicais, com ênfase na leishmaniose tegumentar americana e hanseníase.