Detection of leptospires in biological fluids using DNA hybridisation

DNA extracted from Leptospira interrogans serovar pomona was labelled with phosphorus-32 by nick translation and used as a genomic probe to detect leptospiral DNA. The sensitivity of detection in a 10-microliter spot on nylon membranes was 160 pg of leptospiral DNA or 1.1 X 10(3) leptospires and assays with nylon membranes were somewhat more sensitive than assays with nitrocellulose membranes. The probe reacted with the pathogenic hardjo and tarassovi leptospiral serovars, but not with other genera of bacteria. To detect leptospires in body fluids, these were treated to free leptospiral DNA and then concentrated on membranes using a Bio-Dot apparatus. Neither serum nor urine interfered with the assay system. The DNA of leptospires added to pig urine was stable for at least 2 h at room temperature and for at least 20 h at -20 degrees C.