New spotted fever group Rickettsia isolate, identified by sequence analysis of conserved genomic regions

Abstract

The clinical features of spotted fever group (SFG) Rickettsia induced disease range from a mild to severe illness. The clinical complexity is even greater due to the fact that the disease can be caused by different species with varying degrees of virulence. Current knowledge asserts that the Israeli SFG (ISF) strain Rickettsia conorii israelensis is the only human pathogenic SFG member in Israel. Current diagnostic procedures distinguish between SFG and the typhus group rickettsiosis, assuming all SFG‐positive clinical samples positive for ISF. Molecular studies on questing ticks over the past decade have uncovered the existence of other SFG strains besides ISF in Israel and the region. This study describes the first documented analysis of SFG‐positive samples from Israeli patients with the goal of distinguishing between ISF and non‐ISF SFG strains. We managed to identify a new Rickettsia isolate from three independent clinical samples in Israel which was shown to be an as‐yet unknown SFG member, showing no absolute identity with any known Rickettsia species present in the NCBI database.