Development and validation of a multiplex real-time qPCR assay using GMP-grade reagents for leprosy diagnosis

PLoS Negl Trop Dis. 2022 Feb 18;16(2):e0009850. doi: 10.1371/journal.pntd.0009850. eCollection 2022 Feb.

Abstract

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 Cp 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.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Child
  • Child, Preschool
  • DNA, Bacterial / genetics
  • Female
  • Humans
  • Indicators and Reagents / standards
  • Infant
  • Leprosy / diagnosis*
  • Leprosy / microbiology
  • Male
  • Middle Aged
  • Molecular Diagnostic Techniques / methods*
  • Molecular Diagnostic Techniques / standards
  • Multiplex Polymerase Chain Reaction / methods*
  • Multiplex Polymerase Chain Reaction / standards
  • Mycobacterium leprae / genetics*
  • Mycobacterium leprae / isolation & purification
  • Real-Time Polymerase Chain Reaction / methods*
  • Real-Time Polymerase Chain Reaction / standards
  • Sensitivity and Specificity
  • Young Adult

Substances

  • DNA, Bacterial
  • Indicators and Reagents

Grants and funding

This work was funded by a grants from: Banco Nacional de Desenvolvimento Econômico e Social (BNDES), contract no. 15.2.0473.1 (Operation #4.816.864) to MAK, and Novartis Foundation and Leprosy Research Initiative (LRI; 703.15.45), Foundation for Research Support of the State of Rio de Janeiro (FAPERJ;E-26/203.053/2016), Brazilian National Council for Scientific and Technological Development (CNPq; 421852/2017-2018), Brazilian Coordination for Improvement of Higher Education Personnel (CAPES), and by the National Fund for Health/Brazilian Ministry of Health (MS/SCTIE/DECIT; 404277/2012-8 and TED 145/2018) to MOM. The funders had no participation in the present study’s design, data collection, analysis, interpretation, or writing of the report and decision to submit for publication.