Analysis of Borrelia burgdorferi genotypes in patients with Lyme arthritis: High frequency of ribosomal RNA intergenic spacer type 1 strains in antibiotic-refractory arthritis.

Objective. Most of the Borrelia burgdorferi genotypes have been isolated from erythema migrans (EM) skin lesions in patients with Lyme disease. OspC type K strains, which are 16S-23S ribosomal RNA intergenic spacer type 2 (RST2) strains, are most commonly recovered, but a higher percentage of OspC type A strains (RST1), the next most commonly recovered type, is detectable in blood. The goal of this study was to determine the B burgdorferi genotypes in the joints of patients with Lyme arthritis. Methods. Joint fluid samples from 124 patients seen over a 30-year period were analyzed for OspC types by semi-nested polymerase chain reaction (PCR) and sequencing, and for RSTs by nested PCR and restriction fragment length polymorphism analysis. These results were correlated with clinical outcome. Results. OspC and RST genotypes were identified in 49 of the 124 joint fluid samples (40%). In these 49 samples, OspC type K strains (RST2) were identified in 21 samples (43%), OspC type A strains (RST1) were identified in 11 samples (22%), and 8 other OspC types and all 3 RSTs were identified among the remaining 17 samples (35%). However, among the 17 patients who had been treated with antibiotics according to current guidelines, all 7 patients who were infected with RST1 strains had antibiotic-refractory arthritis, compared with 4 of 6 patients infected with RST2 strains and only I of 4 infected with RST3 strains (P = 0.03). Conclusion. Most of the B burgdorferi genotypes, particularly OspC type K (RST2), were identified in the joint fluid of patients with Lyme arthritis, and the genotype frequencies found in joints reflected those in EM skin lesions. However, RST1 strains were most frequent in patients with antibiotic-refractory arthritis. Our results help to further the understanding of the differential pathogenicity of strains of B burgdorferi.