Incidence of Blastocystis hominis in faecal samples submitted for routine microbiological analysis.

Over a one-year period, 1390 faecal samples were submitted to Aberystwyth Public Health Laboratory for routine microbiological examination. All were stained using a commercial trichrome method. Blastocystis hominis was detected in 96 (6.9%), making it the most common parasite found in the study. Of the B. hominis-positive specimens, 73% were missed on direct microscopy. Molecular typing of B. hominis has revealed extensive genetic diversity in morphologically identical strains and thus detection by microscopy alone may not be sufficient to confirm the role of this organism in human disease.

Detection of Dientamoeba fragilis by culture.

Symptoms associated with Dientamoeba fragilis include diarrhoea, abdominal pain, nausea, vomiting, epigastric pain and weight loss. A possible link between D. fragilis and irritable bowel syndrome (IBS)-like symptoms has been reported, and therefore the presence of this parasite should be excluded before making a diagnosis of IBS. Over a six-month period, 976 faecal samples were submitted to NPHS Microbiology Aberystwyth for routine microbiological analysis. All samples were also cultured for parasites using Robinson's xenic medium. Trichrome staining was undertaken whenever practicable, but many stools had insufficient material. D. fragilis was isolated from 25 (2.6%) patients, whereas Cryptosporidium spp. was detected in 16 (1.6%) patients. D. fragilis was only detected in nine (1.3%) out of 685 specimens stained with trichrome, although four of the 25 culture-positive stools had insufficient sample for staining. Parasite culture proved to be less laborious than trichrome staining and dramatically increased D. fragilis detection rate.