Trichomonads are obligate protozoan symbionts found in the digestive and urogenital tract of vertebrates. They are characterized morphologically by multiple anterior flagella and a single recurrent flagellum that functions as an undulating membrane. Trophozoites reproduce by binary fission and undergo direct transmission from host to host without formation of environmentally stable cysts.1
Genera of the order Trichomonadida consist of commensal and pathogenic species. Pentatrichomonas hominis inhabits the large intestine of a number of mammalian hosts and is considered to be a commensal.2 Trichomonads are occasionally identified in the feces of dogs with diarrhea, where they are presumed to be an opportunistic overgrowth of P hominis.3–12 However, morphologic or molecular means to confirm the identity of these trichomonads is rarely undertaken, and literature on P hominis infection is limited.
Trichomonads other than P hominis have been recognized in the gastrointestinal tract of many species including nonhuman primates,13,14 pigs,15 horses,16 dogs,17 and cattle.18 Recently, intestinal trichomonads associated with diarrheal disease in domestic cats were presumed to be P hominis.19–21 Only by means of molecular characterization and experimental infection studies was the trichomonad identified as Tritrichomonas foetus and determined to be a primary cause of the diarrhea.22,23
Development of a specific means to identify P hominis in dogs with trichomonosis and diarrhea would facilitate recognition of novel and potentially pathogenic species of trichomonads that infect the gastrointestinal tract. Recently, Crucitti et al24 described the use of 2 sensitive and highly specific oligonucleotide probes for the identification of P hominis. However, the authors did not determine the detection limits of PCR assay for detection of P hominis in biological specimens, particularly feces, and experiments to optimize performance of the PCR assay in biological samples were not reported. Fecal samples are considered to be among the most complex specimens for direct PCR testing because of the presence of inherent PCR inhibitors, which are often coextracted along with pathogen DNA.25 The purpose of the study reported here was to determine the optimum reaction conditions and detection limits of PCR assay for identification of P hominis in DNA extracted from canine fecal specimens.
AmericanType Culture Collection
Quality-control strain Pentatrichomonas hominis ATCC 30098, American Type Culture Collection, Rockville, Md.
Medium 2154, American Type Culture Collection, Rockville, Md.
QIAamp DNA mini kit, Qiagen, Valencia, Calif.
Integrated DNA Technologies, Coralville, Iowa.
AmpliTaq Gold DNA polymerase, Applied Biosystems, Foster City, Calif.
New England Biolabs, Beverly, Mass.
iCycler iQ, Bio-Rad Laboratories Ltd, Hercules, Calif.
QIAquick PCR purification kit, Qiagen, Valencia, Calif.
Automated DNA Sequencing Facility, University of North Carolina, Chapel Hill, NC.
QIAamp DNA stool mini kit, Qiagen, Valencia, Calif.
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