title: Clonal diversity of the glutamate dehydrogenase gene in Giardia duodenalis from Thai isolates: evidence of genetic exchange or mixed infections?
abstract: BACKGROUND
  The glutamate dehydrogenase gene (gdh) is one of the most popular and useful genetic markers for the genotypic analysis of Giardia duodenalis (syn. G. lamblia, G. intestinalis), the protozoan that widely causes enteric disease in humans. To determine the distribution of genotypes of G. duodenalis in Thai populations and to investigate the extent of sequence variation at this locus, 42 fecal samples were collected from 3 regions of Thailand i.e., Central, Northern, and Eastern regions. All specimens were analyzed using PCR-based genotyping and recombinant subcloning methods.
  
  
  RESULTS
  The results showed that the prevalence of assemblages A and B among these populations was approximately equal, 20 (47.6%) and 22 (52.4%), respectively. Sequence analysis revealed that the nucleotide diversity of assemblage B was significantly greater than that in assemblage A. Among all assemblage B positive specimens, the allelic sequence divergence within isolates was detected. Nine isolates showed mixed alleles, ranged from three to nine distinct alleles per isolate. Statistical analysis demonstrated the occurrence of genetic recombination within subassemblages BIII and BIV was likely.
  
  
  CONCLUSIONS
  This study supports increasing evidence that G. duodenalis has the potential for genetic exchange.
authors.affiliation: Department of Microbiology, Faculty of Science, Mahidol University, Rama VI Rd,, Bangkok, 10400, Thailand. scptn@mahidol.ac.th
authors.forename: Suradej
authors.initials: S
authors.lastname: Siripattanapipong
authors.forename: Saovanee
authors.initials: S
authors.lastname: Leelayoova
authors.forename: Mathirut
authors.initials: M
authors.lastname: Mungthin
authors.forename: R C Andrew
authors.initials: RC
authors.lastname: Thompson
authors.forename: Parima
authors.initials: P
authors.lastname: Boontanom
authors.forename: Wilai
authors.initials: W
authors.lastname: Saksirisampant
authors.forename: Peerapan
authors.initials: P
authors.lastname: Tan-Ariya
mesh_terms: D000483:Alleles; D002675:Child, Preschool; D060085:Coinfection / Q000469:parasitology*; D005243:Feces / Q000469:parasitology; D005260:Female; D014644:Genetic Variation; D016829:Giardia lamblia / Q000145:classification / Q000201:enzymology* / Q000235:genetics* / Q000302:isolation & purification; D005873:Giardiasis / Q000469:parasitology*; D005969:Glutamate Dehydrogenase / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007223:Infant; D008297:Male; D008969:Molecular Sequence Data; D010802:Phylogeny; D011995:Recombination, Genetic; D013785:Thailand
chemical_list: D005969:Glutamate Dehydrogenase