Molecular evidence for person-to-person transmission of a novel subtype in Giardia duodenalis assemblage B at the rehabilitation institution for developmentally disabled people.

Giardia duodenalis was found in three patients and a health care worker at a rehabilitation institution for developmentally disabled people. The four isolates were genotyped and subtyped by multilocus homology searching and phylogenetic analyses of the following four loci: glutamate dehydrogenase (gdh), triosephosphate isomerase (tpi), and β-giardin (bg) as variable loci, and elongation factor 1 alpha (ef1α) as a conserved locus. The partial sequences, gdh (709 bp), tpi (526 bp), bg (724 bp), and ef1α (680 bp) of four isolates obtained were mutually identical, and the isolates were found to be a novel subtype in sub-assemblage BIV, strongly indicating that person-to-person transmission by a single subtype occurred at the institution.