Isolation of Borrelia miyamotoi and other Borreliae using a modified BSK medium

Borrelia spirochetes are the causative agents of Lyme borreliosis (LB) and relapsing fever (RF). Despite the steady rise in infections and the identification of new species causing human illness over the last decade, isolation of borreliae in culture has become increasingly rare. A modified Barbour-Stoenner-Kelly (BSK) media formulation, BSK-R, was developed for isolation of the emerging RF pathogen, Borrelia miyamotoi. BSK-R is a diluted BSK-II derivative supplemented with Lebovitz's L-15, mouse and fetal calf serum. Decreasing the concentration of CMRL 1066 and other components was essential for growth of North American B. miyamotoi. Sixteen B. miyamotoi isolates, originating from Ixodes scapularis ticks, rodent and human blood collected in the eastern and upper midwestern United States, were isolated and propagated to densities > 10⁸ spirochetes/mL. Growth of five other RF and ten different LB borreliae readily occurred in BSK-R. Additionally, primary culture recovery of 20 isolates of Borrelia hermsii, Borrelia turicatae, Borrelia burgdorferi and Borrelia mayonii was achieved in BSK-R using whole blood from infected patients. These data indicate this broadly encompassing borreliae media can aid in in vitro culture recovery of RF and LB spirochetes, including the direct isolation of new and emerging human pathogens.