BORRELIA RECURRENTIS CHARACTERIZATION AND COMPARISON WITH RELAPSING-FEVER, LYME-ASSOCIATED, AND OTHER BORRELIA SPP

Borrelia recurrentis, the cause of louse-borne relapsing fever, has un til recently been considered noncultivable, which has prevented charac terization of this spirochete, We successfully cultivated 18 strains f rom patients with louse-borne relapsing fever and present the initial characterization of these isolates, Electron microscopy revealed spiro chetal cells with pointed ends, an average wavelength of 1.8 mu m, an amplitude of 0.8 mu m, and 8 to 10 periplasmic flagella. The G+C ratio was 28.4 mol%. Whole DNA-DNA hybridizations showed similarity between the isolates of B. recurrentis but not with Borrelia hermsii, Borreli a parkeri, Borrelia turicatae, or the Lyme-associated borreliae. Seque ncing studies of both the flagellin and 16S RNA genes revealed that th e greatest similarity was between B. recurrentis and Borrelia duttonii , Analysis of the sodium dodecyl sulfate-polyacrylamide gel electropho resis profiles of strains revealed four groups based on tile position of a major protein hand (one of the groups showed some heterogeneity a nd was subdivided into four subgroups), Pulsed-field gel electrophores is revealed five distinct patterns.