Giardia duodenalis: Detection by Quantitative Real-Time PCR and Molecular Diversity

Conventional microscopy is being progressively replaced by molecular (PCR and Sanger sequencing) methods for the first-line detection, identification, and genotyping of diarrhea-causing enteric parasites in modern clinical and research laboratories. These technologies allow increased sample testing, improved throughput, and optimized laboratory workflow in a cost-effective manner. Here, we describe the methodological algorithm used in a national reference center for the diagnosis and molecular characterization of Giardia duodenalis, a major contributor to the enormous burden of diarrheal disease globally. Initial detection of the parasite is conducted by a sensitive real-time PCR to amplify the small subunit of the ribosomal RNA of G. duodenalis, whereas a multilocus sequence genotyping scheme based on three constitutive genetic markers (glutamate dehydrogenase, β-giardin, and triose phosphate isomerase) is used for genotyping and sub-genotyping purposes. The advantages and disadvantages of these PCR-based methods are commented.