LYME BORRELIOSIS Detection and identification of the infecting genotype

Sammanfattning: Lyme borreliosis is caused by the spirochete Borrelia burgdorferi sensu lato, a bacterium with a parasitic life-style, which is transmitted between hosts by the Ixodes tick-vector. Humans will incidentally become infected. The resulting illness can involve the skin, nervous system, joints and heart. Southern Sweden has been identified as an area endemic for Lyme borreliosis. The most common clinical manifestations are erythema migrans and neuroborreliosis. Three major species have been associated with Lyme borreliosis in Europe, B. burgdorferi sensu stricto (s. s.), B. afzelii and B. garinii. The presence of the two latter species was indicated in a seroepidemiological study where a Lyme borreliosis infected population, living in southern Sweden, showed preferential seroreactivity to the species-specific loop of the surface membrane protein P66 originating from B. afzelii and B. garinii. In parallel, a study was performed using culture-based analytical method. Subsequently determination of the OspA serotype (protein-based), and the 16S rDNA genotype, indicated that, B. afzelii (OspA serotype 2) and B. garinii (OspA serotype 5 and 6) were present in skin and cerebrospinal fluid from patients in the region. Using a direct molecular method, that combines nested OspA PCR and sequence analysis, the third major species, B. burgdorferi s. s., was identified in a clinical specimen for the first time in Sweden. In order to further improve the sensitivity and quantification of Borrelia spirochetes, we designed a RT real-time PCR assay directed against 16S rRNA, a method providing both excellent sensitivity and reproducibility. In conclusion, the three major Lyme Borrelia species, B. burgdorferi s. s., B. afzelii and B. garinii, have been found to be associated with Lyme borreliosis in southern Sweden.