AUTHOR=Hashemi-Hafshejani Saeideh , Meamar Ahmad Reza , Moradi Maryam , Hemmati Nasrin , Solaymani-Mohammadi Shahram , Razmjou Elham 

TITLE=Multilocus sequence typing of Giardia duodenalis genotypes circulating in humans in a major metropolitan area

JOURNAL=Frontiers in Medicine

VOLUME=9

YEAR=2022

URL=https://www.frontiersin.org/journals/medicine/articles/10.3389/fmed.2022.976956

DOI=10.3389/fmed.2022.976956

ISSN=2296-858X

ABSTRACT=<p><italic>Giardia duodenalis</italic> is an intestinal protozoan parasite of humans and animal hosts and comprises eight microscopically indistinguishable molecularly-diverse lineages designated as assemblages A–H. Assemblages A and B are the primary sources of infections in humans and a wide range of mammals. Here, we identified assemblages, and inter-/intra-assemblage genetic diversity of human <italic>G. duodenalis</italic> isolates based on the multilocus sequence typing of the triosephosphate isomerase (<italic>tpi</italic>), β -giardin (<italic>bg</italic>), and glutamate dehydrogenase (<italic>gdh</italic>) loci. Multilocus sequence analysis of 62 microscopically-positive <italic>G. duodenalis</italic> fecal samples identified 26 (41.9%), 27 (43.5%), and nine (14.5%) isolates belonging to assemblages A, B, and discordant assemblages, respectively. The <italic>tpi</italic> locus assemblage-specific primers identified dual infections with A and B assemblages (45.2%). The sequence analysis of multiple alignments and phylogenetic analysis showed low genetic polymorphism in assemblage A isolates, classified as sub-assemblage AII at three loci, subtype A2 at <italic>tpi</italic> and <italic>gdh</italic> loci, and subtype A2 or A3 at <italic>bg</italic> locus. High genetic variations were found in assemblage B isolates with 14, 15, and 23 nucleotide patterns at <italic>tpi, bg</italic>, and <italic>gdh</italic> loci, respectively. Further concatenated sequence analysis revealed four multilocus genotypes (MLG) in 24 assemblages A isolates, two previously-identified (AII-1 and AII-5), with one novel multilocus genotype. However, the high genetic variations observed in assemblage B isolates among and within the three genetic loci prevented the definitive designation of specific MLGs for these isolates. Multilocus sequence typing may provide new insight into the genetic diversity of <italic>G. duodenalis</italic> isolates in Tehran, suggesting that humans are likely a potential source of <italic>G. duodenalis</italic> infection. Further host-specific experimental transmission studies are warranted to elucidate the modes of transmission within multiple host populations.</p>