DNA probes and PCR for diagnosis of parasitic infections

Abstract

DNA probe and PCR-based assays to identify and detect parasites are technically complex; however, they have high sensitivity, directly detect parasites independent of the immunocompetence or previous clinical history of the patient, and can distinguish between organisms that are morphologically similar. Diagnosis of parasites is often based on direct detection by microscopy, which is insensitive and laborious and can lack specificity. Most PCR-based assays were more sensitive than DNA probe assays. The development of PCR-based diagnostic assays requires multiple steps following the initial selection of oligonucleotide primers and reporter probe. Generally, the ability to detect the DNA of one parasite was attained by PCR; however, advances in the preparation of samples for PCR (extraction of DNA while removing PCR inhibitors) will be required to achieve that sensitivity with human specimens. Preliminary PCR systems have been developed for many different parasites, yet few have been evaluated with a large number of clinical specimens and/or under field conditions. Those evaluations are essential for determination of clinical and field utility and performance and of the most appropriate application of the assay. Several situations in which PCR-based diagnosis will result in epidemiologic, medical, or public health advances have been identified.

Malaria diagnosis: standardization of a polymerase chain reaction for the detection of Plasmodium falciparum parasites in individuals with low-grade parasitemia

“…Development of a sensitive and specific PCR method for detection of parasites in blood samples requires the establishment of certain criteria, such as the methodology of parasite DNA extraction, oligonucleotides, DNA target selection, and DNA amplification conditions (Weiss 1995).…”

Detection of Toxoplasma gondii DNA in Sheep and Goat Milk in Northwest of Iran by PCR-RFLP

“…The classification is based on their characteristics in electrophoresis of iso-enzymes, PCR-RFLP, random amplified polymorphism DNA (RAPD). 10 - 16 Different strains of T. gondii have different pathogenicity in various animals (e.g. type I is more pathogen in mice).…”

Otitis media and a neck lump – Current diagnostic challenges for Paragonimus-like trematode infections

“…Although advanced diagnostic technologies such as nucleic acid amplification techniques (NAATs) have been developed for many infectious diseases, the incorporation of such tests into clinical parasitology is slow. 15 It would have been desirable to support the clinical diagnosis of Achillurbainia congolensis infection in our patient with definitive diagnostic tests. In the absence of the latter, clinical acumen and awareness of this rare disease presenting 'out of area' were more essential in establishing the correct diagnosis.…”