Background: The characteristics of a Spanish strain of Borrelia burgdorferi, the spirochete which causes Lyme's disease, and which, up to the present, has not been isolated in Spain, are described.
Methods: The organism was obtained from ticks (Ixodes ricinus) from the northern part of Spain. It was studied in culture by dark field microscopy and the internal structure observed by electron transmission. The antigenic composition was analyzed under polyacrylamide electrophoresis, immunoblot and reactivity against monoclonal antibodies. Plasmid analysis was carried out by Southern blot.
Results: In culture the length of the organism is somewhat shorter than normal. It grows slowly and tends to autoagglutinate. It has 6-13 periplasmic flagella. The antigenic analysis of this microorganism through immunoblot and reactivity against different monoclonal antibodies showed differences with regards to other North American strains, with the most significant being the composition of certain proteins of the surface of the organism. These differences may have clinical repercussion. DNA analysis by Southern blot demonstrated slight differences in regard to the composition of plasmids compared to other strains analyzed.
Conclusions: Borrelia burgdorferi exists in Spain. The isolated strain shows peculiar characteristics with respect to others analyzed. The availability of an autochthonous strain may allow more reliable serological diagnosis in Spain.