Molecular identification of Giardia duodenalis in Ecuador by polymerase chain reaction-restriction fragment length polymorphism

Abstract

The aim of this study was to determine the genetic diversity of Giardia duodenalis present in a human population living in a northern Ecuadorian rain forest. All Giardia positive samples (based on an ELISA assay) were analysed using a semi-nested polymerase chain reaction-restriction fragment length polymorphism assay that targets the glutamate dehydrogenase (gdh) gene; those amplified were subsequently genotyped using NlaIV and RsaI enzymes. The gdh gene was successfully amplified in 74 of 154 ELISA positive samples; 69 of the 74 samples were subsequently genotyped. Of these 69 samples, 42 (61%) were classified as assemblage B (26 as BIII and 16 as BIV), 22 (32%) as assemblage A (3 as AI and 19 as AII) and five (7%) as mixed AII and BIII types. In this study site we observe similar diversity in genotypes to other regions in Latin America, though in contrast to some previous studies, we found similar levels of diarrheal symptoms in those individuals infected with assemblage B compared with those infected with assemblage A.

Fig. 1. amplification of the 432 base pairs (bp) band specific for the glutamate dehydrogenase gene of Giardia duodenalis. Lane 1: molecular weight marker 1,000 bp; 2: Giardia positive control 432 bp; 3: Giardia positive 432 bp.

Fig. 2. ethidium bromide stained 2% high-resolution agarose gel showing DNA amplified at the glutamate dehydrogenase for genetic assemblages AII and B digested with Nla IV (A) and genetic assemblages BIII and BIV digested with RsaI (B). Lane 1: molecular weight marker 1,000 base pairs (bp); 2, 5, 6: assemblage B (120 bp, 290 bp); 3, 4: assemblage AII (70 bp, 80 bp, 90 bp, 120 bp); 7: molecular weight marker 1,000 bp; 8, 9: assemblage BIII (130 bp, 300 bp); 10, 11: assemblage BIV (430 bp).