We repeatedly detected DNA of Borrelia garinii or B. afzelii and Borrelia-like structures in the blood, joint fluid or in the synovium of 10 patients with
Lyme arthritis by means of the polymerase chain reaction and immunoelectron microscopy at 2-4-month intervals in the course of two years. All samples were analyzed using primers which amplified the 16S rRNA gene sequence of Borrelia burgdorferi sensu lato and nucleotide sequences for the OspA gene. No cross hybridization occurred with DNA from human cells and with DNA from other bacteria. Capture and labelling with monoclonal antibodies of aggregated antigens, membranes and flagellae were evident in the blood of 7 patients, in 4 synovial membranes and 2 synovial fluids. Borreliae were found in blood capillaries, in collagen and in clusters surrounding inflammatory cells in the synovium of patients with recurrent infections who carried IgM and IgG antibodies to OspA and to 83 kDa core protein. After significant improvement for several weeks after treatment, arthritis recurred in six patients. Synoviocyte hyperplasia, inflammatory infiltration and concentric adventitial fibroplasia were seen in the synovium of the patients with persisting borreliae. Only two patients were infected with B. afzelii, the others with B. garinii.