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      Detection of Mycobacterium leprae in Ocular Tissues by Histopathology and Real-Time Polymerase Chain Reaction

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          Aim: To report detection of leprosy in ocular tissue by histopathology and its confirmation by genetic analysis. Methods: Excised tissue from a clinically-suspected ocular leprosy patient was processed and analyzed histopathologically. The DNA from the paraffin-embedded tissue was extracted, an 85 A-C intergenic region of Mycobacterium leprae was amplified using specific primers and analyzed by conventional as well as real-time polymerase chain reaction (RT-PCR). Results: With periodic acid-Schiff-hematoxylin (PAS-H) staining the specimen showed presence of a thin fibrinous layer of inflammatory cells. The majority of the tissue was fibrovascular with extensive infiltration by histiocytes having reticulated cytoplasm. Modified PAS-H and acid-fast staining (AFS) showed the presence of several acid-fast organisms within the cytoplasm of histiocytes and mast cells. Conventional PCR showed a 250-bp DNA from excised conjunctival tissue, which was in agreement with the positive controls for M. leprae. Through RT-PCR, it was calculated that the suspected tissue had 44.68 pg of M. leprae DNA, which is 8937.06 genome copies of M. leprae. Conclusions: Presence of inflammatory cells and AFS bacilli in tissue presented a typical picture of leprosy. M. leprae DNA can be detected using RT-PCR in ocular tissues when acid-fast bacteria are seen in histopathological sections. And when the diagnosis of leprosy is inconclusive and acid-fast bacteria are seen, RT-PCR for M. leprae DNA could be used as a rapid confirmatory test to identify the presence of M. leprae and, therefore, the diagnosis of leprosy.

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          Most cited references 10

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          Simple and fast lateral flow test for classification of leprosy patients and identification of contacts with high risk of developing leprosy.

          The interruption of leprosy transmission is one of the main challenges for leprosy control programs since no consistent evidence exists that transmission has been reduced after the introduction of multidrug therapy. Sources of infection are primarily people with high loads of bacteria with or without clinical signs of leprosy. The availability of a simple test system for the detection of antibodies to phenolic glycolipid-I (PGL-I) of Mycobacterium leprae to identify these individuals may be important in the prevention of transmission. We have developed a lateral flow assay, the ML Flow test, for the detection of antibodies to PGL-I which takes only 10 min to perform. An agreement of 91% was observed between enzyme-linked immunosorbent assay and our test; the agreement beyond chance (kappa value) was 0.77. We evaluated the use of whole blood by comparing 539 blood and serum samples from an area of high endemicity. The observed agreement was 85.9% (kappa = 0.70). Storage of the lateral flow test and the running buffer at 28 degrees C for up to 1 year did not influence the results of the assay. The sensitivity of the ML Flow test in correctly classifying MB patients was 97.4%. The specificity of the ML Flow test, based on the results of the control group, was 90.2%. The ML Flow test is a fast and easy-to-perform method for the detection of immunoglobulin M antibodies to PGL-I of M. leprae. It does not require any special equipment, and the highly stable reagents make the test robust and suitable for use in tropical countries.
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            Evaluation of real-time and conventional PCR targeting complex 85 genes for detection of Mycobacterium leprae DNA in skin biopsy samples from patients diagnosed with leprosy.

            In spite of the decrease in the number of registered leprosy patients, the number of new cases diagnosed each year (400,000) has remained essentially unchanged. Leprosy diagnosis is difficult due to the low sensitivity of current methodologies to identify new cases. In this study, conventional and TaqMan real-time PCR assays for detection of Mycobacterium leprae DNA were compared to current classification based on clinical, bacteriological, and histological evaluation. M. leprae DNA was extracted from frozen skin biopsy specimens from 69 leprosy patients enrolled in the study and was amplified using specific primers for either the antigen 85B-coding gene or the 85A-C intergenic region by using conventional and real-time PCR. The detection rate was 100% among multibacillary (MB) patients and ranged from 62.5% to 79.2% among paucibacillary (PB) patients according to the assay used. The TaqMan system for 85B gene amplification showed the highest sensitivity, although conventional PCR using the 85A-C gene as a target was also efficient. The cycle threshold (C(T)) values obtained using the TaqMan system were able to statistically (P < 0.0001) differentiate MB (mean C(T), 28.06; standard deviation [SD], 4.51) from PB (mean C(T), 33.06; SD, 2.24) patients. Also, there was a correlation between C(T) values and the bacteriological index for MB patients (Pearson's r, -0.444; P = 0.008). Within the PB patients' group, we tested normal skin from six patients exhibiting the pure neuritic form of leprosy (PNL). Five out of six PNL patients were positive for the presence of M. leprae DNA, even in the absence of skin lesions. In conclusion, the TaqMan real-time PCR developed here seems to be a useful tool for rapidly detecting and quantifying M. leprae DNA in clinical specimens in which bacilli were undetectable by conventional histological staining.
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              Detection of Mycobacterium leprae in nasal mucosa biopsies by the polymerase chain reaction.

              Several discoveries about leprosy indicate that Mycobacterium leprae transmission mainly occurs by inhalation, and the nose is major port of entry and exit. The present study evaluated the clinical application of PCR for detection of M. leprae DNA in nasal mucosa biopsies in untreated leprosy patients (52) and their contacts (99) from the State Reference Center in Sanitary Dermatology and Leprosy, Uberlandia, MG, Brazil. PCR detection of a 372-base pair DNA fragment from M. leprae was accomplished in 36 (69.2%) patients, from which 34 (91.9%) of them were multibacillaries. Furthermore, PCR was positive in 3 (16.7%) of 18 slit-skin smear negative, 4 (25.0%) of 16 skin lesion BI negative, 8 (33.3%) of 24 nasal mucosa BI negative patients, and 10 of 99 contacts (10.1%). The presence of bacilli in 10.1% of the contacts may potentially reflect an occult leprosy, and these patients must be accompanied, followed by a chemoprophylaxy treatment. Considering all PCR results against clinical and BI classification of patients and controls, we have found a sensitivity of 69.2%, a specificity of 89.9%, and an accuracy of 82.8%. It has been demonstrated here through PCR of nasal biopsies that the bacillus invades the mucosa, passing through the nasal inferior turbinate to reach peripheral blood. Therefore, the molecular investigation of invasive nasal biopsies by PCR tests has proven to be useful in defining patients of higher risk of transmission and risk-group contacts, which is an important step to reach the World Health Organization objective towards the elimination of leprosy as a public health problem.

                Author and article information

                Ophthalmic Res
                Ophthalmic Research
                S. Karger AG
                March 2007
                08 February 2007
                : 39
                : 2
                : 63-68
                aResearch Department, bOculoplastic & Orbital Division, and cPathology Department, King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia; dFIOCRUZ, Laboratório de Hanseníase, Departamento de Micobacterioses, Manguinhos, Rio de Janeiro, Brazil
                99375 Ophthalmic Res 2007;39:63–68
                © 2007 S. Karger AG, Basel

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                Page count
                Figures: 3, References: 33, Pages: 6
                Original Paper


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