Two rickettsial isolates recovered from Ixodes ricinus ticks in Puy-de-Dôme (Central France) were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Western blot immunoassay, restriction fragment length polymorphism analysis, and sequencing of a portion of the citrate-synthase gene. By these methods, the isolates appeared to be identical to a member of the spotted fever group rickettsiae, Rickettsia helvetica. This first isolation of Rickettsia helvetica in France has epidemiologic importance; a serosurvey on Mediterranean spotted fever conducted previously in Puy-de-Dôme, where the infection is not endemic, demonstrated a high seroprevalence of nonspecific antibodies directed against spotted fever group rickettsiae lipopolysaccharides, and thus the possibility of infection due to a rickettsia different from Rickettsia conorii was suggested. The isolation of Rickettsia helvetica in anthropophilic ticks in the same area further supports this hypothesis.
Granulocytic ehrlichia 16S rDNA was amplified for the 1st time from an Ixodes ricinus (Linne) tick collected in Europe. Sequence analysis of polymerase chain reaction products from the 16S rRNA gene demonstrated the organism from which it originated to be closely related to the agent of human granulocytic ehrlichiosis, an emerging disease that was recently described in the United States; Ehrlichia phagocytophila, the agent of tick-borne fever of ruminants in Europe; and Ehrlichia equi. the agent of the worldwide equine granulocytic ehrlichiosis. These granulocytic ehrlichiae have been associated with Ixodes spp. ticks that may act as vectors. It remains to be determined if each of these granulocytic ehrlichiae, that may constitute variants of the same species, is responsible for a specific disease in animals and in humans.
Two rickettsial isolates recovered from Ixodes ricinus ticks in Puy-de-Dôme (Central France) were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Western blot immunoassay, restriction fragment length polymorphism analysis, and sequencing of a portion of the citrate-synthase gene. By these methods, the isolates appeared to be identical to a member of the spotted fever group rickettsiae, Rickettsia helvetica. This first isolation of Rickettsia helvetica in France has epidemiologic importance; a serosurvey on Mediterranean spotted fever conducted previously in Puy-de-Dôme, where the infection is not endemic, demonstrated a high seroprevalence of nonspecific antibodies directed against spotted fever group rickettsiae lipopolysaccharides, and thus the possibility of infection due to a rickettsia different from Rickettsia conorii was suggested. The isolation of Rickettsia helvetica in anthropophilic ticks in the same area further supports this hypothesis.
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