Vaidação de método molecular para identificação de Mycobacterium leprae em amostras de sangue

Abstract

Leprosy is a chronic infectious disease with slow evolution and a difficult diagnosis and, therefore, often late, with the etiological agent, the bacillus Mycobaterium leprae, already causing some degree of physical disability. The treatment of the disease depends on the clinical form of the disease, whether multibacillary or paucibacillary. Due to its high endemicity in Brazil, the second country in the world in new cases of leprosy, different forms of diagnosis that are more effective and faster than the clinical diagnosis are sought. This study is justified in the identification of a molecular test of lower cost, with a sample of easy access that allows an early diagnosis, based on the analysis of blood samples of contacts younger than 15 years and without necessarily presenting suspicious lesions. To validate the SYBR Green Real-Time Polymerase Chain Reaction (qPCR) diagnostic method, targets from specific regions of M. leprae, RLEP and 16SrRNA, were used to perform analytical specificity and sensitivity tests. To evaluate the frequency of positivity of the method, blood samples collected from index cases and contacts from three endemic municipalities were used. In the tests, high sensitivity and specificity were found for the method, especially for the RLEP target, which presented a lower detection rate and specificity of 100%, presenting better results than qPCR method already validated for the diagnosis of leprosy in samples of skin lesion biopsy, the NAT Hanseníase. As for the frequency of positivity, there was a low rate among patients, therefore it was expected due to the disease being well established and undergoing treatment, while for contacts, significant results were found for the risk of developing the disease between PB and MB contacts, however, it was necessary to monitor these patients to verify the evolution of the condition, which was not possible due to the COVID 19 pandemic. It is clear that more longitudinal and continuity studies are needed, using the SYBR Green method between contacts to assess the test's diagnostic sensitivity.