IDENTIFICATION OF A NOVEL RICKETTSIAL INFECTION IN A PATIENT DIAGNOSED WITH MURINE TYPHUS

Identification of ELB agent-infected fleas and rodents within several foci of murine typhus in the United States has prompted a retrospectiv e investigation for this agent among human murine typhus patients. Thi s agent is a recently described rickettsia which is indistinguishable from Rickettsia typhi with currently available serologic reagents. Mol ecular analysis of the 17-kDa antigen gene and the citrate synthase ge ne has discriminated this bacterium from other typhus group and spotte d fever group rickettsiae. Current sequencing of its 16S ribosomal DNA gene indicates a homology of 98.5% with R. typhi and 99.5% with R. ri ckettsii. Through a combination of restriction fragment length polymor phism and Southern hybridization analysis of rickettsia-specific PCR p roducts, one of five tested patient blood samples was shown to be infe cted with ELB while R. typhi infections were confirmed in the remainin g samples. This is the first reported observation of a human infection by the ELB agent and underscores the utility of PCR-facilitated diagn osis and discrimination of these closely related rickettsial infection s.