[Genotyping of Giardia intestinalis strains isolated from humans in Aydin, Turkey]

Giardia intestinalis which is a flagellate, intestinal protozoon of humans and a variety of mammalian species, shows worldwide distribution. To date, eight genotypes of the parasite have been identified. Among these genotypes, assemblage A and B have zoonotic characteristics with low host specificity, thus they are responsible for the human infections. The aim of this study was to identify G.intestinalis genotypes in Aydin, located in Aegean region of Turkey. A total of 40 stool samples that were found positive for G.intestinalis by direct microscopic examination, from Adnan Menderes University, Research and Training Hospital, Parasitology Laboratory from January 2011 to December 2014 were included in the study. DNA isolation from stool samples performed with commercial kit (QIAamp DNA Stool Mini Kit, Qiagen, Germany) followed by polymerase chain reaction (PCR) for G.intestinalis 16S rRNA and beta-giardin genes and then the amplicons were sequenced. Out of 40 isolates 11 (27.5%) were positive with 16S rRNA PCR and 10 (25%) were positive with beta-giardin PCR. Of 21 sequenced amplicons, 10 (47.6%) of them showed 98%-100% similarity with reference sequences and their genotypes could be identified. The distribution of genotypes were as follows: cluster A1 (n: 3), cluster A2 (n: 3), cluster A3 (n: 2) and assemblage B (n: 2). In the light of our results the isolates detected in humans might be zoonotic origin. In accordance with the previous reports in Turkey, assemblage A (8/10) was more common than assemblage B (2/10). In the present study, 10 (25%) out of 40 isolates could be genotyped and sequencing of beta-giardin gene yielded more effective results than sequencing of 16S rRNA for the determination of assemblages. The present study indicated that, there is a need for prospective studies with extended number of cases allowing the comparison of the two genes used for G.intestinalis genotyping.