DEVELOPMENT OF AN IMMUNOMAGNETIC ANTIGEN CAPTURE SYSTEM FOR DETECTINGLEPTOSPIRES IN BOVINE URINE

A magnetic bead antigen capture system which combined the use of two e volving techniques-immunomagnetic separation (IMS) and time-resolved f luoroimmunoassay (TR-FIA)-was developed to detect Leptospira borgpeter senii serovar hardjo in bovine urine. The assay utilised monoclonal an tibody coated magnetic beads to capture leptospiral antigen which was in turn detected using another monoclonal antibody (Indicator) labelle d with biotin. Signal was generated by the binding of europium labelle d streptavidin to indicator antibody. The sensitivity of the assay was improved from 10(3) to 10(2) leptospires per mi by using: an ethanol precipitation procedure to treat each sample. The assay detected only 31 of 56 (55 per sent) urine specimens culture-positive for hardjo, bu t seven of 24 urine samples culture-negative for hardjo were identifie d as positive by the assay. These seven samples were from animals whic h were culture positive on at least one other occasion. These results suggest that this system should be further investigated as a complemen tary test to culture for the identification of hardjo carrier animals.