Molecular genetic analysis ofGiardia intestinalisisolates at the glutamate dehydrogenase locus

Abstract

SUMMARYSamples of DNA from a panel ofGiardiaisolated from humans and animals in Europe and shown previously to consist of 2 major genotypes–‘Polish’ and ‘Belgian’–have been compared with human-derived Australian isolates chosen to represent distinct genotypes (genetic groups I–IV) defined previously by allozymic analysis. Homologous 0·52 kilobase (kb) segments of 2 trophozoite surface protein genes (tsa417 and tsp11, both present in isolates belonging to genetic groups I and II) and a 1·2 kb segment of the glutamate dehydrogenase (gdh) gene were amplified by the polymerase chain reaction (PCR) and examined for restriction fragment length polymorphisms (RFLPs). Of 21 ‘Polish’ isolates that were tested, all yieldedtsa417-like andtsp11-like PCR products that are characteristic of genetic groups I or II (15 and 6 isolates respectively) in a distinct assemblage ofG. intestinalisfrom Australia (Assemblage A). Conversely, most of the 19 ‘Belgian’ isolates resembled a second assemblage of genotypes defined in Australia (Assemblage B) which contains genetic groups III and IV. RFLP analysis ofgdhamplification products showed also that ‘Polish’ isolates-were equivalent to Australian Assemblage A isolates (this analysis does not distinguish between genetic groups I and II) and that ‘Belgian’ isolates were equivalent to Australian AssemblageB isolates. Comparison of nucleotide sequences determined for a 690 base-pair portion of thegdhPCR products revealed ≥ 99·0% identity between group I and group II (Assemblage A/‘Polish’) genotypes, 88·3–89·7% identity between Assemblage A and Assemblage B genotypes, and ≥ 98·4% identity between various Assemblage B/‘Belgian’ genotypes. The results confirm that theG. duodenalisisolates examined in this study (inclusive ofG. intestinalisfrom humans) can be divided into 2 major genetic clusters: Assemblage A (= ‘Polish’ genotype) containing allozymically defined groups I and II, and Assemblage B (= ‘Belgian’ genotype) containing allozymically defined groups III and IV and other related genotypes.

Molecular typing ofGiardia duodenalisin humans in Queensland – first report of Assemblage E

“…The only two previous studies, which analysed a small number of Giardia isolates from Queensland, identified both assemblage A and B (Nolan et al 2011;Ebner et al 2015). Analysis of genetic variability within assemblages has shown that isolates of assemblage A can be divided into four sub-assemblages (AI, AII, AIII and AIV) by protein polymorphisms of 23 loci (Monis et al 1996(Monis et al , 2003, with human isolates belonging to AI and AII and animal isolates belonged to AI, AIII and AIV (Monis et al 2003;Cacciò et al 2008;Sprong et al 2009;Ryan and Cacciò, 2013). In the present study, although there was 100% concordance between loci in assignment to assemblage, there were some differences in assignment to sub-assemblage level.…”

Comparative evaluation ofGiardia duodenalissequence data

“…The typical applications of these loci have therefore varied accordingly. For Giardia the conserved SSU rDNA is traditionally used for species and assemblage/subassemblage level genotyping (Sogin et al 1989 ;van Keulen et al 1991van Keulen et al , 1993van Keulen et al , 1995Hopkins et al 1997), where as the most variable locus, tpi, is frequently used for subtyping clinical samples (Lu et al 1998 ;Amar et al 2002) and the gdh locus, with a substitution rate midway between them, has a broad application spectrum (Monis et al 1996(Monis et al , 1999.…”

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Genotyping of Giardia in Dutch patients and animals: A phylogenetic analysis of human and animal isolates

“…Infection occurs by faecal oral route transmission, either by direct contact or by ingestion of contaminated food or water (Monis and Thompson, 2003). Despite morphological uniformity, considerable biotypic and genetic diversity exists within the G. duodenalis species (Monis et al, 1996 andThompson et al, 2000). The species includes several 'assemblages' or genotypes, A-G, that can be discriminated on the basis of host selection and genomic mutations (Monis et al, 1999).…”