Use of an immuno-peroxidase staining method for the detection of Entamoeba histolytica in stool samples in endemic areas

The detection of Entamoeba histolytica in stool and tissue samples or in culture has been hampered by several constraints that are related to traditional microscopic examination of fresh samples and those stained with other chemical reagents. In this study, a direct immunoperoxidase (DIP) technique was used for the identification of E. histolytica in stool samples and compared to direct microscopy and permanent staining. Immunopurified antigens of axenic E. histolytica were used to produce rabbit hyper-immune sera. Immunoglobulin G (IgG) was purified from hyper-immune sera and coupled to peroxidase using a two-step procedure. The IgG-peroxidase conjugate was then evaluated by detection of E. histolytica in 128 stool samples and 20 controls from different hospitals in Cameroon, using a direct immunoperoxidase method. The trophozoïtes and cysts of E. histolytica were strongly stained; both intact and damaged cysts or vegetative forms could be detected in all the positive samples. The immunoperoxidase method was more specific than the iron haematoxylin with no significant difference in sensitivity between the two methods. Results from this study demonstrated that the DIP staining is a reliable, specific and rapid method for the diagnosis of E. histolytica infections. Keywords: amoebiasis, diagnosis, direct immuno-peroxidase, Entamoeba histolytica, Entamoeba dispar, endemic areas, parasites Journal of Tropical Microbiology and Biotechnology Vol. 2(1) 2006: 10-1