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Molecular typing of Giardia duodenalis in humans in Queensland – first report of Assemblage E
- ZAHEDI, ALIREZA, FIELD, DANIEL, RYAN, UNA
- Parasitology 2017 v.144 no.9 pp. 1154-1161
- Giardia lamblia, feces, genes, genetic variation, glutamate dehydrogenase, humans, loci, mixed infection, parasites, quantitative polymerase chain reaction, sequence analysis, triose-phosphate isomerase, Queensland
- Little is known about the genetic diversity of the protozoan parasite, Giardia duodenalis, infecting humans in Queensland, Australia. The present study typed 88 microscopically Giardia-positive isolates using assemblage-specific primers at the triose phosphate isomerase (tpi) gene and sequenced a subset of isolates at the glutamate dehydrogenase (gdh) gene (n = 30) and tpi locus (n = 27). Using the tpi-assemblage specific primers, G. duodenalis assemblage A and assemblage B were detected in 50% (44/88) and 38·6% (34/88) of samples, respectively. Mixed infections with assemblages A and B were identified in 4·5% (4/88) and assemblage E was identified in 6·8% (6/88) of samples. Sequence analysis at the gdh and tpi loci also confirmed the presence of assemblage E in these isolates. Cyst numbers per gram of feces (g⁻¹) were determined using quantitative polymerase chain reaction and of the isolates that were typed as assemblage E, cyst numbers ranged 13·8–68·3 × 10⁶ cysts g⁻¹. This is the first report of assemblage E in humans in Australia, indicating that in certain settings, this assemblage may be zoonotic.