Growth of Leptospira pomona and Its Effect on Various Tissue Culture Systems

Miller, Robert E. (University of Nebraska College of Medicine, Omaha), Norman G. Miller, and Roberta J. White. Growth of Leptospira pomona and its effect on various tissue culture systems. J. Bacteriol. 92:502-509. 1966.-Leptospira pomona strain 3341 was grown in association with primary fetal bovine kidney (PBK) and human embryonic skin-muscle fibroblastic (HE) cells in Eagle's minimal essential medium (MEM) with 5% sheep serum. Growth curves of leptospires in PBK and HE cell cultures showed no substantial increase in growth above that obtained in Eagle's MEM in the absence of tissue culture cells. This suggested that no stimulatory growth factors for leptospires were produced by the tissue cells. Fibroblastic cells of the PBK monolayer showed separation, deterioration, and, finally, complete disintegration. Epithelial-like cells remained unaffected. HE cells showed the same cytopathic effect as PBK fibroblastic cells, indicating that this effect was not limited to PBK fibroblastic cells. Warthin-Starry stains of PBK and HE cell monolayers showed masses of leptospires adhering to fibroblastic cells, whereas only a few were seen on epithelial-like cells. Large numbers of leptospires on the surface of fibroblastic cells are very likely associated with the cytopathic effect. Dislodgment of leptospires from fibroblastic cells did not increase the total number of spirochetes in the culture. This indicated that leptospiral growth did not occur on the surface of these cells.