Related Experiment Video
Updated: Jul 9, 2026
A Multi-detection Assay for Malaria Transmitting Mosquitoes
Published on: February 28, 2015
Development and evaluation of a triplex real-time PCR assay for enhanced plague diagnostics in Madagascar
Beza Ramasindrazana1,2, Zoé A Rahalison1,3, Philippe Gauthier4
1Plague Unit, Institut Pasteur de Madagascar, Antananarivo, Madagascar.
Background:
The plague, caused by Yersinia pestis, remains a critical public health issue, particularly in endemic regions like Madagascar. Rapid and accurate detection of this pathogen is essential for effective outbreak management and timely intervention. Following the urban plague outbreak of 2017, a new molecular diagnostic algorithm was developed and introduced into routine use. However, certain cases required combining real-time and conventional polymerase chain reaction (PCR) methods. While effective, this approach often delayed obtaining conclusive results, an issue that can hinder swift outbreak responses. The aim of this study is to design and optimize a three-target real-time PCR assay (qPCR) for the detection of Y. pestis in clinical samples.
Methods:
The assay targeted three genes: caf1, pla, and yopM, located on the plasmids pMT1, pPCP1, and pCD1, respectively. Conducted at the Institut Pasteur de Madagascar (IPM), the study evaluated the assay using both pure bacterial cultures and clinical samples, including 50 bubonic aspirates and 50 respiratory specimens.
Results:
Using bacteriology technique as the reference standard, the triplex qPCR demonstrated a sensitivity of 100% (89-100%) and a specificity of 82%. The positive predictive value (PPV) was 73% and the negative predictive value (NPV) was 100% (91-100%). The coefficient of agreement kappa was 0.74, with a p-value of <0.0001. Notably, the new assay resolved 100% of previously inconclusive cases from the duplex qPCR test targeting only pla and caf1.
Discussion:
While a new plague diagnostic algorithm has been set up after the outbreak in 2017, the present study suggests a real-time PCR assay based on three genes to improve the speed and accuracy of plague diagnostic. Furthermore, this new technique is a valuable tool for managing plague outbreaks and supporting field diagnostics not only in Madagascar but also in countries with plague.
Conclusions:
The developed triplex assay to molecularly diagnose Y. pestis in human samples improves the standard already in place and allows to resolve ambiguities previously associated with inconclusive results from duplex qPCR tests, thereby reinforcing the reliability and accuracy of this new technique. Implementing this new method into routine will enable a faster, more effective response to plague outbreaks by reducing the time needed to confirm plague cases and limiting the spread of the diseases. This new technique is also flexible and can be undertaken close to human cases with adequate biosecurity and biosafety measures.
Insights
A new three-target real-time PCR assay accurately detects Yersinia pestis, improving plague diagnostics. This method resolves inconclusive results, enabling faster outbreak response and disease control.
Area of Science:
- Molecular diagnostics
- Infectious disease epidemiology
- Public health microbiology
Background:
- Plague, caused by Yersinia pestis, is a significant public health concern in endemic areas.
- Current diagnostic methods, including real-time and conventional PCR, can lead to delayed results.
- A need exists for rapid and accurate Y. pestis detection to manage outbreaks effectively.
Purpose of the Study:
- To design and optimize a three-target real-time PCR (qPCR) assay for Y. pestis detection.
- To enhance the speed and accuracy of plague diagnostics in clinical samples.
Main Methods:
- Developed a triplex qPCR assay targeting three Y. pestis genes: caf1, pla, and yopM.
- Evaluated the assay using pure bacterial cultures and clinical samples (bubonic aspirates and respiratory specimens).
Main Results:
- The triplex qPCR showed 100% sensitivity and 82% specificity against bacteriology.
- Achieved 100% positive and negative predictive values for previously inconclusive cases.
- Demonstrated strong agreement (kappa = 0.74, p < 0.0001) with the reference standard.
Conclusions:
- The triplex qPCR assay improves upon existing plague diagnostic algorithms.
- This method enhances diagnostic reliability by resolving ambiguities from duplex qPCR tests.
- Implementation facilitates faster outbreak response and disease control in endemic regions and beyond.
