A singleplex real-time fluorescence resonance energy transfer PCR with melting curve analysis for the differential detection of Paragonimus heterotremus, Echinostoma malayanum and Fasciola gigantica eggs in faeces.

Background: Because the eggs of Paragonimus, Echinostoma and Fasciola are very similar in size and shape, it is difficult to distinguish and accurately identify species by the morphology of their eggs, which is a standard diagnostic method.

Methods: In this study, a novel assay combining a real-time fluorescence resonance energy transfer PCR and melting curve analysis using one set of primers and fluorophore-labelled hybridization probes specific for the 28S rDNA region was developed for the molecular detection of Paragonimus heterotremus, Echinostoma malayanum and Fasciola gigantica eggs.

Results: This assay could detect and distinguish P. heterotremus, E. malayanum and F. gigantica DNA with the distinct melting temperature (Tm) values of 57.99±0.08, 62.12±0.15 and 74.10±0.18, respectively. The assay can also be used to detect and distinguish DNA from P. bangkokensis, P. harinasutai, P. machorchis, E. revolutum, Hypodereum conoideum and F. hepatica, which have different Tm values. The sensitivity of this assay enabled the detection of one egg of P. heterotremus, E. malayanum or F. gigantica per 100 mg of faeces. In addition, the specificity testing showed no fluorescence signal for other parasites.

Conclusions: Due to the sensitivity and specificity of our assay in detecting P. heterotremus, E. malayanum and F. gigantica, our method could be used to accurately diagnose these three medically important parasitic groups and has potential implications for molecular epidemiological investigations of human and/or animal infections.