Clonal diversity of the glutamate dehydrogenase gene in Giardia duodenalisfrom Thai Isolates: evidence of genetic exchange or Mixed Infections?

Siripattanapipong, Suradej; Leelayoova, Saovanee; Mungthin, Mathirut; Thompson, RC Andrew; Boontanom, Parima; Saksirisampant, Wilai; Tan‐ariya, Peerapan

doi:10.1186/1471-2180-11-206

Cited by 22 publications

(19 citation statements)

References 38 publications

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“…Despite the fact that Giardia is believed to be a strictly clonal (asexual) organism, there is evidence for recombination at the telomeres (but not the internal regions) of some of the chromosomes of the parasite [9,56]. Additional evidence of genetic recombination has been demonstrated at the cellular level in cultured assemblage B trophozoites and in cysts from clinical samples [57], and at the population level within sub-assemblages BIII and BIV [58]. Taken together, these findings may explain the occurrence of discordant genotypes BIII/BIV, as those described in the present survey.…”

Section: Discussionmentioning

confidence: 99%

Multilocus genotyping of Giardia duodenalis in Southwestern Iran. A community survey

et al. 2020

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Giardia duodenalis is one of the main enteric pathogens associated with diarrheal disease. In developing countries, giardiasis is a major public health concern, particularly in children under five years of age. This study aimed to evaluate the occurrence and genetic diversity of G. duodenalis causing human infections in Shushtar County, Southwestern Iran. Individual faecal specimens were collected from 1,163 individuals (male/female ratio: 0.9; age range 2-75 years) with (n = 258) and without (n = 905) gastrointestinal symptoms living in rural and urban settings during the period 2017-2018. Conventional (sucrose flotation and microscopy) methods were used for the initial detection of G. duodenalis cysts in faecal specimens. Microscopy-positive samples were confirmed by PCR amplification and sequencing of the small subunit rRNA (ssu rRNA) gene of the parasite. A multilocus genotyping (MLG) scheme targeting the triose phosphate isomerase (tpi), the glutamate dehydrogenase (gdh), and the beta-giardin (bg) genes was used for genotyping purposes. Giardia duodenalis cysts were detected in 7.7% (90/1,163) of samples by microscopy, of which 82 were confirmed by ssu-PCR. Successful amplification and sequencing results were obtained for 23.2% (19/82), 9.8% (8/82), and 8.5% (7/82) of the confirmed samples at the tpi, gdh, and bg loci, respectively. MLG data for the three loci were available for two samples only. Out of the 24 samples genotyped at any loci, 50% (12/24) were identified as assemblage A and the remaining half as assemblage B. Overall, AII was the most prevalent sub-assemblage detected (41.7%, 10/ 24), followed by BIII (25.0%, 6/24), discordant BIII/BIV (5/24) or AII/AIII (2/24) sequences, and BIV (1/24). No significant correlation was demonstrated between a given assemblage/ sub-assemblage and the occurrence of clinical symptoms. No genotypes adapted to animal hosts other than humans (e.g. assemblages C-F) were found circulating in the investigated human population, suggesting that transmission of human giardiasis in this Iranian region is primarily of anthroponotic nature. Further molecular-based studies are needed to confirm and expand these results, and to ascertain the presence and public health relevance of the parasite in environmental (e.g. drinking water) samples.

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Section: Discussionmentioning

confidence: 99%

Multilocus genotyping of Giardia duodenalis in Southwestern Iran. A community survey

et al. 2020

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“…duodenalis in the cyst stage) leading to gene conversion or crossing-over events can most likely achieve this effect [ 52 ], raising the question of whether Giardia is also capable of sexual reproduction. Indeed, evidence of genetic recombination has been demonstrated at the cellular level in cultured assemblage B trophozoites and in cysts from clinical samples [ 53 ], and at the population level within sub-assemblages BIII and BIV [ 47 ]. However, somewhat conflicting results are currently available regarding the potential exchange of genetic material between genotypes of different G .…”

Section: Discussionmentioning

confidence: 99%

Prevalence and Genetic Diversity of Giardia duodenalis and Cryptosporidium spp. among School Children in a Rural Area of the Amhara Region, North-West Ethiopia

et al. 2016

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BackgroudGiardia duodenalis and Cryptosporidium spp. are enteric protozoan causing gastrointestinal illness in humans and animals. Giardiasis and cryptosporidiosis are not formally considered as neglected tropical diseases, but belong to the group of poverty-related infectious diseases that impair the development and socio-economic potential of infected individuals in developing countries.MethodsWe report here the prevalence and genetic diversity of G. duodenalis and Cryptosporidium spp. in children attending rural primary schools in the Bahir Dar district of the Amhara Region, Ethiopia. Stool samples were collected from 393 children and analysed by molecular methods. G. duodenalis was detected by real-time PCR, and the assemblages and sub-assemblages were determined by multilocus sequence-based genotyping of the glutamate dehydrogenase and β-giardin genes of the parasite. Detection and identification of Cryptosporidium species was carried out by sequencing of a partial fragment of the small-subunit ribosomal RNA gene.Principal FindingsThe PCR-based prevalences of G. duodenalis and Cryptosporidium spp. were 55.0% (216/393) and 4.6% (18/393), respectively. A total of 78 G. duodenalis isolates were successfully characterized, revealing the presence of sub-assemblages AII (10.3%), BIII (28.2%), and BIV (32.0%). Discordant typing results AII/AIII and BIII/BIV were identified in 7.7% and 15.4% of the isolates, respectively. An additional five (6.4%) isolates were assigned to assemblage B. No mixed infections of assemblages A+B were found. Extensive genetic variation at the nucleotide level was observed within assemblage B (but no within assemblage A), resulting in the identification of a large number of sub-types. Cryptosporidium diversity was demonstrated by the occurrence of C. hominis, C. parvum, and C. viatorum in the population under study.ConclusionsOur data suggest an epidemiological scenario with an elevated transmission intensity of a wide range of G. duodenalis genetic variants. Importantly, the elevated degree of genetic diversity observed within assemblage B is consistent with the occurrence of intra-assemblage recombination in G. duodenalis.

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“…0.00235 vs. 0.00340 for assemblage A and 0.00433 vs. 0.00620 for assemblage B. Another study from Thailand based on gdh gene [ 24 ] also showed significant higher nucleotide divergence (K) in assemblage B than assemblage A. In the context of the overall worldwide comparison, assemblage B yielded the highest level of genetic diversity followed by assemblage E and assemblage A.…”

Section: Discussionmentioning

confidence: 99%

“…Populations that have been stable over time are expected to have a bimodal and multimodal mismatch distribution [ 37 – 39 ]. However, the influence of selection could be locus-dependent as test for neutrality from other studies suggested that the bg gene was possibly influenced by ongoing purifying selection [ 23 ] while the gdh gene was under neutral selection [ 24 ]. On the other hand, if Giardia undergoes reproduction asexually as it is generally assumed, the population would be made up of independently evolving lineages and mutations are expected to confine to the lineage in which they began [ 11 ], thereby the different rate of mutation with selection pressure might contribute to the excess polymorphism sites but low frequency of haplotype and limit its potential of evolution.…”

Section: Discussionmentioning

confidence: 99%

Population expansion and gene flow in Giardia duodenalis as revealed by triosephosphate isomerase gene

et al. 2015

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BackgroundGiardia duodenalis is a protozoan parasite that can cause significant diarrhoeal diseases. Knowledge of population genetics is a prerequisite for ascertaining the invasion patterns of this parasite. In order to infer evolutionary patterns that could not be uncovered based on the morphological features, a population genetic study with the incorporation of molecular marker was carried out to access the genetic structure of G. duodenalis isolated from the Malaysian population and the global populations.MethodsA total of 154 samples positive for Giardia, collected from different Malaysian communities, were subjected to DNA amplification and sequencing targeting three genetic loci (tpi, gdh, and bg). The tpi sequences together with sequences from the global data obtained from the NCBI GenBank were used for genetic diversity analyses including identification of haplotypes, haplotype diversity, nucleotide diversity, Tajima’s D and Fu and Li’s D, gene flow and genetic differentiation tests.ResultsAnalysis of the Malaysian and global data showed that assemblages A, B, and E (the most prevalent assemblages in humans and animals), have different levels of genetic diversity. Assemblage B had the highest level of both haplotype diversity and nucleotide diversity, followed by assemblage E. The analysis also revealed population expansion and high gene flow in all assemblages. No clear genetic structure was observed across five continents (i.e., the Americas, Europe, Asia, Australia and Africa). However, median joining network of assemblage B formed a cluster that was exclusively isolated from Asia while other haplotypes were well dispersed across the continents.ConclusionsThis study provides new insight into the genetic diversity of Giardia assemblages in different geographical regions. The significant result shown by gene flow and genetic differentiation analyses as well as test of neutrality among the populations should have brought a clearer picture to the dynamics and distribution of Giardia infection.

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Clonal diversity of the glutamate dehydrogenase gene in Giardia duodenalisfrom Thai Isolates: evidence of genetic exchange or Mixed Infections?

Cited by 22 publications

References 38 publications

Multilocus genotyping of Giardia duodenalis in Southwestern Iran. A community survey

Multilocus genotyping of Giardia duodenalis in Southwestern Iran. A community survey

Prevalence and Genetic Diversity of Giardia duodenalis and Cryptosporidium spp. among School Children in a Rural Area of the Amhara Region, North-West Ethiopia

Population expansion and gene flow in Giardia duodenalis as revealed by triosephosphate isomerase gene

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