Molecular Differences between Several Species of Strongyloides and Comparison of Selected Isolates of S. stercoralis Using a Polymerase Chain Reaction-Linked Restriction Fragment Length Polymorphism Approach

Srinivasan RamachandranClinical Parasitology Unit, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland

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Albert A. GamClinical Parasitology Unit, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland

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Franklin A. NevaClinical Parasitology Unit, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland

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The relationships between the parasitic nematodes of medical importance belonging to the genus Strongyloides was studied using a polymerase chain reaction (PCR)-linked restriction fragment length polymorphism approach. We used several human and dog isolates of S. stercoralis, a monkey isolate of S. fulleborni, and S. ratti, a rodent parasite. The molecular analysis was based on amplification of the internal transcribed spacer and the 5′ portion of the 23S-like rRNA gene followed by restriction enzyme digests. The length of the PCR product was specific to each species and varied around 1.5 kilobase pairs. Using nine restriction enzymes, we were able to analyze both interspecific and intraspecific variations. With four restriction enzymes (Taq I, Dde I, Dra I, and Mwo I), human isolates of S. stercoralis from different parts of the world showed identical patterns and could be differentiated from the dog isolate of S. stercoralis. Interspecific differences were readily observed with these and other enzymes. In addition to providing new information on the genomic characteristics of Strongyloides parasites, the results suggest that this technique could be useful for diagnostic and epidemiologic investigations.

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