Molecular typing of Giardia duodenalis in humans in Queensland - first report of Assemblage E

摘要

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 x 10(6) 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.