Two; major genotypic assemblages of Giardia intestinalis infect humans; the nested real-time polymerase chain reaction (PCR) was used for targeting the triose phosphate isomerase (tpi) gene to detect and genotype G. intestinalis in human feces in Egypt. Among 97 fecal samples, 30 (31%) were diagnosed as giardiasis by saline wet mount microscopy after staining with Lugol's iodine. The tpi gene was amplified from 41 (42.3%) fecal samples, of which 11 were microscopy-negative specimens. Of the total samples, 24 (58.5%) contained assemblage A group I, and 7 (17.1%) were assemblage A group II from the group of patients complaining of intermittent diarrhea. Eight (19.5%) samples contained assemblage B from patients with persistent diarrhea. Two (5%) samples had a mixture of assemblage A group II and assemblage B. The technique was able to detect as few as 20 trophozoites per PCR on fecal DNA-isolated, microscopy-negative, and quantitative (q)PCR-positive specimens; there was a higher average cycle threshold value than microscopy-positive and qPCR-positive specimens, suggesting that they represented true, low-burden infections. In conclusion, we could genotype G. intestinalis from fresh stool samples in Egypt; in infections commonly presented with intermittent diarrhea, the most prevalent genotype was assemblage A group I. The most vulnerable age group included 10-to 20-yr-old individuals.In developing countries of Asia, Africa, and Latin America, approximately 200 million people have symptomatic giardiasis (Thompson et al., 2000;Yason and Rivera, 2007). Giardia intestinalis is the most prevalent cause of parasitic diarrhea in the developed world, and this infection is also very common in developing countries. Moreover, there is an association of Giardia species and strain assemblages with diarrhea/dysentery (Haque, 2007).In Egypt, Foronda et al. (2008) found that assemblage B was the most prevalent (80%) genotype, with another 15% of the positive samples belonging to assemblage E, and 5% to assemblage A. Transmission of the G. intestinalis cyst to humans occurs mainly after ingestion of contaminated water, autoinfection, and person-to-person contact. Clinical manifestations of symptomatic giardiasis include greasy stools, flatulence, diarrhea, abdominal cramps, epigastric tenderness, as well as steatorrhea accompanied by full-blown malabsorption syndrome (Gardner and Hill, 2001). However, the majority of cases are asymptomatic or minimally symptomatic in immunocompetent individuals (Furness et al., 2000).Species of Giardia can be distinguished on the basis of morphology, ultrastructural features, or the 16S rRNA sequence; there are at least 6 species, i.e., G. intestinalis (5lamblia), G. agilis, G. muris, G. ardeae, G. psittaci, and G. microti (Monis et al., 1999). Among the 6 species, G. intestinalis infects humans and numerous other mammals (Thompson et al., 2000). Isolates of G. intestinalis are classified into 7 assemblages, based on the characterization of the glutamate dehydrogenase, small-subunit rR...
