Leprosy Diagnosis: An Update on the Use of Molecular Tools Lucrecia

Abstract

Leprosy is a chronic infectious disease caused by an obligatory intracellular mycobacteria Mycobacterium leprae, which presents tropism for Schwann cells and skin macrophages. Leprosy is a public health problem and early diagnosis is essential to avoid incapacities. The disease´s clinical presentation varies from few to widespread lesions and its diagnosis continues to be a challenge due to the low sensibility of the conventional methods, based on bacillary counts of skin smears and histopathology. Molecular techniques, especially the methods to identify M. leprae DNA based on polymerase chain reaction (PCR) have emerged as a support of the conventional methods for the analysis of clinical samples in difficult to diagnose cases, such as pure neural leprosy, indeterminate and paucibacillary leprosy. The technique has also proved useful in the study of leprosy transmission and monitoring résistance to the WHO recommended Multidrug treatment. Different biological samples can be analysed and there is no consensus in the molecular diagnostic techniques respect of the most efficient nucleic acid extraction method, most appropriate methodology and genetic target for PCR. These methods provide a very valuable option for confirmation of difficult clinical cases with scarce bacilli but requires a well-equipped laboratory and the high cost makes it inaccessible to be used as a routine diagnostic tool in most endemic countries.

Evaluation of Auramine O staining and conventional PCR for leprosy diagnosis: A comparative cross-sectional study from Ethiopia

“…ZN is uncomplicated, cost-effective and the most frequently used method for the detection of AFB especially in resource limited settings. The sensitivity of ZN is inconsistent ranging from 18% to 56%, depending on the study [ 23 – 25 , 43 ].We reported a sensitivity of 59.3% respectively, with a low negative predictive value demonstrating the probable high rate of false negative for ZN. An acceptable alternative would be AO staining on SSS with a slightly higher percentage of positivity (64.9%, p >0.05).…”

“…PCR is often acknowledged for its great sensitivity among all laboratory diagnostic tests [ 22 , 23 ]. A study in Brazil reported PCR sensitivity of 40% for TT, 55.5% for BT and 100% for all BB, BL and LL cases, respectively [ 44 ].…”

Diagnosis and Management of Leprosy

“…M. leprae investigation by PCR has been done with various samples, such as swabs, fragment biopsy, or skin biopsy, nasal swab, urine, nerve, lymph nodes, and hair. 7,20,34,35,36,37 Leprosy is treated with MDT WHO (1998, 2012). The MDT regimen is adjusted according to the type of disease, PB, and MB.…”

Recent Trends in System-Scale Integrative Approaches for Discovering Protective Antigens Against Mycobacterial Pathogens

“…In fact, the advances in M. leprae structural and functional genomics has allowed the development of highly specific PCR-based gene amplification assays for early rapid M. leprae DNA detection with high sensitivity. PCR has also proved useful in the M. leprae viability determination, identification of routes of transmission and leprosy drug resistance ( Geluk et al, 2012 ; Martinez et al, 2014 ; Soto and Muñoz, 2015 ; Maltempe et al, 2016 ).…”