Application of 16S rRNA next generation sequencing in ticks in Greece

Tick-borne bacteria pose a significant threat to human and veterinary public health. Greece is a Mediterranean country with rich tick fauna and the most commonly detected tick-borne bacterial pathogens are members of the Rickettsia and Anaplasma species. The variable V2-V4 and V6-V9 regions of 16S rRNA gene of seven ticks belonging to four genera representative in Greece (Ixodes, Rhipicephalus, Dermacentor, Haemophyssalis) were analysed using multiple primer pairs by next generation sequencing (NGS). Nine bacterial phyla corresponding to 95 families, 116 genera and 172 species were identified. Proteobacteria was the predominant phylum in five of the seven ticks, followed by Actinobacteria, which predominated in two ticks. The tick-borne bacteria included Rickettsia and Anaplasma species, while "Candidatus Midichloria mitochondrii" were detected in high abundance in I. ricinus ticks and less in Rhipicephalus bursa; Coxiella-like endosymbionts were detected in Rh. sanguineus, H. parva, and less in Rh. bursa ticks. Co-infections with Rickettsia and Anaplasma were also observed. 16S rRNA NGS is a powerful tool to investigate the tick bacteriome and can improve the strategies for prevention and control of tick-borne diseases.