Differentiation of Entamoeba histolytica and E. dispar DNA from cysts present in stool specimens by polymerase chain reaction: its field application in the Philippines |
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Authors: | Windell L Rivera Hiroshi Tachibana Mary Rose Agnes Silva-Tahat Haruki Uemura H Kanbara |
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Institution: | (1) Department of Protozoology, Institute of Tropical Medicine, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852, Japan fax: (81) 958-49-7805, JP;(2) Department of Infectious Diseases, Tokai University School of Medicine, Bohseidai, Isehara, Kanagawa 259-11, Japan fax: (81) 463-95-5450, JP |
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Abstract: | It has been established that two distinct species exist within what was originally known as Entamoeba histolytica. These are E. dispar and E. histolytica, for the nonpathogenic and pathogenic forms, respectively. Differentiation of these two organisms is of great clinical importance
since they are morphologically indistinguishable and both forms can infect the human intestinal cavity to different degrees.
A simple and rapid DNA-extraction method that can be used directly on formalin-fixed stool specimens has been developed. The
extracted DNA was used for the identification of the species existing in the stools by polymerase chain reaction (PCR). A
total of 72 randomly collected stool samples from the Philippines were analyzed. In all, 19 samples reacted with E. dispar primers, resulting in the expected 101-bp PCR products; however, none reacted with E. histolytica primers. Furthermore, sensitivity assay suggests that genomic DNA from as few as five cysts can be used as a template for
PCR. These observations imply that the use of genomic DNA directly extracted from formalin-fixed stool specimens for PCR amplification
is a useful tool for obtaining a sensitive and accurate diagnosis that can be applied even in epidemiology studies.
Received: 10 December 1995 / Accepted: 3 April 1996 |
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