Multi-locus Genotyping Reveals High Occurrence of Mixed Assemblages in Giardia duodenalis within a Limited Geographical Boundary

Abstract

Aim: To determine the common genotypes of Giardia duodenalis causing diarrhea in the study region and to assess the extent of genetic polymorphism among them. Study Design: Stool samples were collected from the patients attending IDBG Hospital, Kolkata with diarrheal complaints through a systemic sampling technique and were screened for Giardia duodenalis. The G. duodenalis positive samples were subjected to molecular genotyping through ‘PCR - Direct DNA sequencing’ procedure. All the sequence data obtained were incorporated into MEGA 4 software for multiple alignment and validation followed by phylogenetic analysis. The genotyping data obtained are stored in Excel spreadsheets and incorporated into EpiInfo 3.1 for analyzing possible association of genotype outcome with common physical factors such as age, sex etc. Place and Duration of Study: Department of parasitology, National Institute of Cholera and Enteric Diseases, Kolkata, India from July 2009 to November 2011. Methodology: A total of 68 Giardia duodenalis positive stool samples were identified from the diarrhea patients attending IDBG hospital in the city and were subjected to multi-locus genotyping. Fragments of ß-giardin, Glutamate-dehydrogenase and Triosephosphate-isomerase genes of Giardia were amplified from those samples with specific primers and sequenced. All the sequences were analyzed using MEGA 4 software for obtaining the genotyping results. Results: Multi-locus genotyping identified 13 isolates as assemblage A and 41 as assemblage B, whereas 14 of them could not be assigned in a particular group. Detailed phylogenetic analysis revealed that multiple genotypes were observed in those 14 isolates depending upon the marker loci. Conclusion: The study could produce a preliminary idea about the G. duodenalis genotypes found in Kolkata city. High percentage of mixed assemblages in the study population also revealed the presence of genetic diversity among a small population of diarrheal patient within a limited geographical boundary. It has also hypothesized the possibility of inter-assemblage genetic exchange among Giardia.