Search

Borrelia spp. are transmitted to humans by the bite of an infected tick. In Europe, Borrelia afzelii and Borrelia garinii are the main causative agents of Lyme borreliosis, one of the most prevalent tick-borne diseases in the northern hemisphere. In bacteria such as Borrelia spp., a restriction-modification system (RMS) protects against the harmful introduction of foreign DNA. The RMS comprises two activities: methyltransferase and endonuclease. This study is aimed to characterize the RMS of B. afzelii and B. garinii . First, we identified potential RMS genes. The predicted genes were cloned into a methylase-deficient Escherichia coli strain and digested with methylation-sensitive restriction enzymes to verify methyltransferase activity. Additionally, the RMS proteins were purified to evaluate endonuclease activity. Subsequently, methylated and unmethylated plasmids were used to investigate the effect of methylation on endonuclease activity and transformation efficiency. We identified four possible RMS genes in B. afzelii and four RMS genes in B. garinii . We analyzed the presence of these genes in patient isolates and observed a high degree of heterogeneity. The restriction pattern of DNA methylated by each of the four recombinantly expressed genes provided strong evidence that all encode adenine-specific methyltransferases. After 24 h of incubation with purified RMS proteins, we observed complete digestion of unmethylated plasmid DNA, demonstrating endonuclease activity. Finally, we proved that methylation protects against endonuclease activity and increases transformation efficiency.

Ixodes ricinus is the most relevant vector for tick-borne diseases in Austria and responsible for the transmission of Borrelia burgdorferi sensu lato (s. l.), which causes Lyme borreliosis in humans; however, also other bacteria and protozoa can be found in ticks and have the potential of infecting people and animals. In this study we collected ticks in popular recreational areas in the city of Vienna in the years 2019 and 2020 and analyzed them for the presence of such putative pathogenic microorganisms. By using reverse line blot (RLB) hybridization we detected DNA of B. burgdorferi s. l., Rickettsia spp., Babesia spp., Candidatus Neoehrlichia mikurensis (CNM) and Anaplasma phagocytophilum. Moreover, we also screened them for the relapsing fever spirochete Borrelia miyamotoi employing real-time PCR. The most frequently detected pathogens were B. burgdorferi s. l. in 28.6% of the ticks in 2019 and 21.3% of the ticks in 2020. The genus Rickettsia was detected in 13.8% of the ticks from 2019 and only in 4.6% from 2020. Babesia spp. were detected in 5.7% in 2019 and 4.2% in 2020. Furthermore, we detected CNM in 4.0% (2019) and 5.6% (2020), A. phagocytophilum in 0.5% (2019) and 1.3% (2020) and finally B. miyamotoi in 3.3% (2019) and 1.7% (2020). Collectively, we show that various microorganisms are prevalent in ticks collected in Vienna and identify hotspots for B. miyamotoi, which we have detected for the first time in the city., (© 2022. The Author(s).)