Comparison of microscopy, two xenic culture techniques, conventional and real-time PCR for the detection of Dientamoeba fragilis in clinical stool samples.
Dientamoeba fragilis is a pathogenic protozoan parasite that is notoriously difficult to diagnose. The aim of this study was to determine the gold standard for laboratory detection of D. fragilis. A total of 650 human faecal samples were included in the study. All specimens underwent the following: microscopy using a permanent stain (modified iron-haematoxylin), culture using a modified Boeck and Drbohlav's medium (MBD) and TYGM-9, a conventional polymerase chain reaction (PCR) and a real-time PCR (RT-PCR). The overall prevalence of D. fragilis in the study population was 5.4% (35/650). RT-PCR detected 35 isolates, conventional PCR detected 15 isolates, MBD culture detected 14 isolates, TYGM-9 detected ten isolates, while microscopy detected 12 isolates. RT-PCR detected an additional 15 positive samples compared to the other diagnostic methods, all of which were confirmed by sequencing. When all methods were compared to each other, RT-PCR showed a sensitivity and specificity of 100 and 100%, conventional PCR 42.9 and 100%, MBD culture 40 and 100%, TYGM-9 culture 28.6 and 100%, and microscopy 34.3 and 99%, respectively. These results show that RT-PCR is the diagnostic method of choice for the detection of D. fragilis in clinical samples and, as such, should be considered as the gold standard for diagnosis.
Division of Microbiology, St. Vincent's Hospital, Darlinghurst, NSW, Australia. dstark@stvincents.com.au
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Stark
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Barratt
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Roberts
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Marriott
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Harkness
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Ellis
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D018929:Cell Culture Techniques / Q000379:methods; D002648:Child; D002675:Child, Preschool; D019411:Clinical Laboratory Techniques / Q000379:methods*; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D004029:Dientamoeba / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification*; D004030:Dientamoebiasis / Q000175:diagnosis* / Q000469:parasitology; D005243:Feces / Q000469:parasitology*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008853:Microscopy / Q000379:methods*; D008875:Middle Aged; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA; D055815:Young Adult
D016054:DNA, Protozoan