Significance of Blastocystis hominis in patients referred for bacteriological stool culture at EHNRI
Background: The pathogenic potential of the parasite Blastocystis hominis is often considered controversial. However, it is now gaining acceptance as a human intestinal parasitic agent showing different clinical symptoms.
Objective: To determine the prevalence and related clinical manifestation of B. hominis infection in patients referred for bacteriological stool culture at the Ethiopian Health & Nutrition Research Institute (EHNRI).
Methods: A total of 152 patients referred for bacteriological stool culture to the bacteriology and parasitology labs at EHNRI, were examined for possible infection with B. hominis. A single stool sample from each individual was collected and processed for isolation of bacteria by using a standard culture method for enteric bacteria, while direct and formol-ether concentration methods were used for the detection of ova and parasites; and the Modified Ziehl Neelsen method was applied for Cryptosporidium parvum and Isospora belli and water-ether sedimentation with Uvitex-2B staining method was used for detecting intestinal microsporidia. Clinical information was recorded during stool sample collection.
Results: One Salmonella spp., two Shigella spp. and one case of Escherichia coli were isolated. Blastocystis hominis was detected in 71(46.7%) of the 152 patients examined and 51/71(71.8%) of the patients were found to have been infected with B. hominis alone. Well known opportunistic intestinal parasites - Cryptosporidium parvum 11(7.2%), Isospora belli 13 (8.6%) and Enterocytozoon bieneusi 2 (1.3 %) - were also recorded. Among the helminths, Strongyloides stercoralis 5 (3.3 %) was identified to be the most prevalent. The most common clinical symptoms significantly associated with B. hominis were distension, flatulence and anorexia (P<0.05). Among the positive cases, four staff members (three males aged 38, 40 and 45 years old and one female aged 42 years old) who were infected with B. hominis alone were treated with metronidazole 250 mg, 2 tablets three times a day for 10 days, and responded favourably and all clinical symptoms resolved.
Conclusions: This information is expected to strengthen the newly emerging perception on the pathogenic potential of B. hominis infection. It will also create an awareness of laboratory technicians and physicians for proper diagnosis and management of the disease. From this and other related studies conducted elsewhere, it could be concluded that treating B. hominis infections where defined symptoms are presented with large numbers of parasites in the stool and in the absence of other cases of the disease is recommendable. [Ethiop.J.Health Dev. 2006;21(1):61-67]