High frequency of M. leprae DNA detection in asymptomatic household contacts

Abstract

BackgroundCharacterization of the Mycobacterium leprae genome has made possible the development of Polymerase Chain Reaction (PCR) systems that can amplify different genomic regions. Increased reliability and technical efficiency of quantitative PCR (qPCR) makes it a promising tool for early diagnosis of leprosy. Index cases that are multibacillary spread the bacillus silently, even before they are clinically diagnosed. Early detection and treatment could prevent transmission in endemic areas.MethodsIn this study, the qPCR technique is used to detect DNA of M. leprae in samples of slit skin smears (SSS) of the ear lobe and blood of leprosy patients and their asymptomatic household contacts residing in Governador Valadares, MG, Brazil, a hyperendemic area for leprosy. A total of 164 subjects participated in the study: 43 index cases, 113 household contacts, and, as negative controls, 8 individuals who reported no contact with patients nor history of leprosy in the family. The qPCR was performed to amplify 16S rRNA fragments and was specifically designed for M. leprae.ResultsOf asymptomatic household contacts, 23.89% showed bacillary DNA by qPCR in samples of SSS and blood. Also, 48.84% of patients diagnosed with leprosy were positive for qPCR while the bacillary load was positive in only 30.23% of patients. It is important to note that most patients were already receiving treatment when the collection of biological material for qPCR was performed. The level of bacillary DNA from household contacts was similar to the DNA levels detected in the group of paucibacillary patients.ConclusionConsidering that household contacts comprise a recognizable group of individuals with a high risk of disease, as they live in close proximity to a source of infection, qPCR can be used to estimate the risk of progress towards leprosy among household contacts and as a routine screening method for a chemoprophylactic protocol.Electronic supplementary materialThe online version of this article (10.1186/s12879-018-3056-2) contains supplementary material, which is available to authorized users.

Functional biomarker signatures of circulating T-cells and its association with distinct clinical status of leprosy patients and their respective household contacts

“…Previous reports from our group have also demonstrated the presence of M. leprae DNA in scrapes and blood samples as well as high levels of antibodies to M. leprae recombinant proteins in household contacts [26,27]. These ndings strongly suggest the subclinical infection in household contact.…”

Functional biomarker signatures of circulating T-cells and its association with distinct clinical status of leprosy patients and their respective household contacts

“…Previous reports from our group have also demonstrated the presence of M. leprae DNA in scrapes and blood samples as well as high levels of antibodies to M. leprae recombinant proteins in household contacts [26,27]. These ndings suggest that household contact should be monitored for putative subclinical infection.…”

The role of an active surveillance strategy of targeting household and neighborhood contacts related to leprosy cases released from treatment in a low-endemic area of China

“…Hastings RC group has described increasing family clustering as the endemicity level reduces since 1994 [ 30 ], which means in the low endemic area of Shandong province, surveillance of the RFT patients and their contact individuals is much more important. Numerous studies show that individuals living with a patient with untreated leprosy have a higher risk of developing clinical disease [ 6 , 31 ]. A 25-year follow-up research study in Sulawesi, Indonesia showed that 28 of 101 (28%) newly diagnosed patients were identified as household contacts and 36 (36%) identified as neighbors [ 8 ].…”