SYBR Green real-time PCR-RFLP assay targeting the plasmodium cytochrome B gene--a highly sensitive molecular tool for malaria parasite detection and species determination

PLoS One. 2015 Mar 16;10(3):e0120210. doi: 10.1371/journal.pone.0120210. eCollection 2015.

Abstract

A prerequisite for reliable detection of low-density Plasmodium infections in malaria pre-elimination settings is the availability of ultra-sensitive and high-throughput molecular tools. We developed a SYBR Green real-time PCR restriction fragment length polymorphism assay (cytb-qPCR) targeting the cytochrome b gene of the four major human Plasmodium species (P. falciparum, P. vivax, P. malariae, and P. ovale) for parasite detection and species determination with DNA extracted from dried blood spots collected on filter paper. The performance of cytb-qPCR was first compared against four reference PCR methods using serially diluted Plasmodium samples. The detection limit of the cytb-qPCR was 1 parasite/μl (p/μl) for P. falciparum and P. ovale, and 2 p/μl for P. vivax and P. malariae, while the reference PCRs had detection limits of 0.5-10 p/μl. The ability of the PCR methods to detect low-density Plasmodium infections was then assessed using 2977 filter paper samples collected during a cross-sectional survey in Zanzibar, a malaria pre-elimination setting in sub-Saharan Africa. Field samples were defined as 'final positive' if positive in at least two of the five PCR methods. Cytb-qPCR preformed equal to or better than the reference PCRs with a sensitivity of 100% (65/65; 95%CI 94.5-100%) and a specificity of 99.9% (2910/2912; 95%CI 99.7-100%) when compared against 'final positive' samples. The results indicate that the cytb-qPCR may represent an opportunity for improved molecular surveillance of low-density Plasmodium infections in malaria pre-elimination settings.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cytochromes b / genetics*
  • Genes, Protozoan*
  • Humans
  • Malaria / diagnosis*
  • Malaria / parasitology*
  • Plasmodium / classification
  • Plasmodium / genetics*
  • Polymorphism, Restriction Fragment Length*
  • RNA, Ribosomal, 18S
  • Real-Time Polymerase Chain Reaction* / methods
  • Real-Time Polymerase Chain Reaction* / standards
  • Reproducibility of Results
  • Sensitivity and Specificity

Substances

  • RNA, Ribosomal, 18S
  • Cytochromes b

Grants and funding

Funding provided by Swedish International Development Agency (SIDA) [grant number SWE 2009-193], http://www.sida.se, AM, The Swedish Civil Contingencies Agency (MSB) [grant number 2010-7991], http://www.msb.se, AM, The Swedish Medical Research Council (VR) [grant number 2009-3785], http://www.vr.se, AB and Goljes foundation, http://www.lindhes.se/stiftelseforvaltning/ansokan-om-bidrag, UM. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.