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.
Stark
D
D
Division of Microbiology, St. Vincent's Hospital, Darlinghurst, NSW, Australia. dstark@stvincents.com.au
Barratt
J
J
Roberts
T
T
Marriott
D
D
Harkness
J
J
Ellis
J
J
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