ISOLATION, CULTIVATION, AND PARTIAL CHARACTERIZATION OF THE ELB AGENTASSOCIATED WITH CAT FLEAS

ELB rickettsiae from cat flea homogenates were recovered in tissue cul ture cells following sequential passage through laboratory rats and th e yolk sacs of embryonated chicken eggs. Seven days after inoculation of ELB from the infected yolk sacs, Vero cells and L999 cells were obs erved to contain intracellular bacteria as demonstrated by Diff Quik a nd indirect immunofluorescence assay staining, The rickettsial and ELB identity of the cultured agent was confirmed by PCR detection of the 16S rRNA and citrate synthase genes and PCR-restriction fragment Lengt h polymorphism analysis of the 17-kDa conserved rickettsial antigen ge ne. The ELB rickettsiae induced plaques in Vero cells on day 11 postin fection, Rat anti-ELB serum reacted at 1:4,096 to cultured ELB and had lower reactivity to Rickettsia typhi Wilmington (1:1,024), Rickettsia akari Kaplan (1:512), and Rickettsia australis JC (1:64). Spotted fev er group polyclonal sera also exhibited lower reactivity to ELB than t o the homologous antigen. Coomassie blue-stained sodium dodecyl sulfat e-polyacrylamide gel electrophoresis profiles of the ELB isolate and t wo R. typhi strains were identical.