Urinary excretion of an unidentified treponeme in a case of leptospirosis.

Two kinds of spirochetes were observed by dark-field microscopy in the urine of a leptospirosis patient on day 26 after the onset of the disease. The spirochetes were identified as treponemes and leptospires. A classification of the treponemes on basis of their morphology was attempted by means of electron microscopy with no conclusive result. Cultivation of the spirochetes was unsuccessful. Sera obtained prior to, during and after the excretion of spirochetes were tested for antibodies in routine serology tests for leptospirosis and syphilis. The diagnosis leptospirosis was confirmed by a rise and subsequent fall in antibody titres. The sera were nonreactive in syphilis serology tests, but showed a weak fluorescence in a fluorescent treponemal antibody absorption (FTA-ABS) test when Treponema calligyrum was used as antigen. It could not be determined whether this reaction was due to antibodies raised in response to antigens of the excreted treponemes.