The Isolation of Strains of Rickettsiae of the Spotted Fever Group in Israel and their Differentiation from other Members of the Group by Immunofluorescence Methods

Abstract

Infections with rickettsiae of the spotted fever group have been known to appear in Israel for over 20 years. However, in no case has there been a report on the appearance of the primary lesion typical of all other spotted fever infections except for Rocky Mountain spotted fever. Attempts were therefore made to isolate the local etiologic agents and to compare their antigenic composition with other members of the groups with the aid of immunofluorescence techniques. Three isolates were studied, 2 from dog ticks collected in the field, and 1 from the blood of a human infection. All 3 isolates appeared to be antigenically identical, but differed from the other strains of rickettsiae studied. Using indirect staining procedures all antisera reacted with all members of the group, but showed significant differences in titer against homologous strains and some of the heterologous ones. In those cases in which these differences were not significant, cross-inhibition of staining with homologous and heterologous soluble antigens permitted differentiation. Differences in antigenic composition were also found among strains identified as Rickettsia conori isolated in different geographical areas but not among those isolated in the same area, indicating the possible usefulness of this method for epidemiologic studies.