title: Sequence variability in the first internal transcribed spacer region within and among Cyclospora species is consistent with polyparasitism.
abstract: Cyclospora cayetanensis is a coccidian parasite which causes severe gastroenteritis in humans. Molecular information on this newly emerging pathogen is scarce. Our objectives were to assess genetic variation within and between human-associated C. cayetanensis and baboon-associated Cyclospora papionis by examining the internal transcribed spacer (ITS) region of the ribosomal RNA operon, and to develop an efficient polymerase chain reaction- (PCR)-based method to distinguish C. cayetanensis from other closely related organisms. For these purposes, we studied C. cayetanensis ITS-1 nucleotide variability in 24 human faecal samples from five geographic locations and C. papionis ITS-1 variability in four baboon faecal samples from Tanzania. In addition, a continuous sequence encompassing ITS-1, 5.8S rDNA and ITS-2 was determined from two C. cayetanensis samples. The results indicate that C. cayetanensis and C. papionis have distinct ITS-1 sequences, but identical 5.8S rDNA sequences. ITS-1 is highly variable within and between samples, but variability does not correlate with geographic origin of the samples. Despite this variability, conserved species-specific ITS-1 sequences were identified and a single-round, C. cayetanensis-specific PCR-based assay with a sensitivity of one to ten oocysts was developed. This consistent and remarkable diversity among Cyclospora spp. ITS-1 sequences argues for polyparasitism and simultaneous transmission of multiple strains.
authors.affiliation: Department of Medicine, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: C
authors.initials: C
authors.lastname: Olivier
authors.forename: S
authors.initials: S
authors.lastname: van de Pas
authors.forename: P W
authors.initials: PW
authors.lastname: Lepp
authors.forename: K
authors.initials: K
authors.lastname: Yoder
authors.forename: D A
authors.initials: DA
authors.lastname: Relman
mesh_terms: D000818:Animals; D001483:Base Sequence; D021744:Cyclospora / Q000737:chemistry / Q000145:classification / Q000235:genetics*; D021866:Cyclosporiasis / Q000469:parasitology; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics*; D014644:Genetic Variation; D006801:Humans; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction / Q000379:methods; D012340:RNA, Ribosomal, 5.8S / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity; D012407:rRNA Operon / Q000235:genetics
chemical_list: D016054:DNA, Protozoan; D004275:DNA, Ribosomal; D021903:DNA, Ribosomal Spacer; D012340:RNA, Ribosomal, 5.8S