Following the course of human leptospirosis: evidence of a critical threshold for the vital prognosis using a quantitative PCR assay

In order to follow the course of acute human leptospirosis, an ELISA microt iter plate hybridization method was developed for the quantitative determin ation of Leptospira spp. in biological samples after PCR. The biotin-labell ed amplified product (331 bp from the rrs ae, ne) was hybridized with a com plementary capture probe covalently linked onto animated polystyrene wells, and detected using a colorimetric reaction. The mean detection limit was 5 0 copies per 10 mul. In a prospective study of human leptospirosis cases, w e obtained evidence that a density of 10(4) leptospires per ml of blood is a critical threshold for the vital prognosis of the patients. The practicab ility of the method makes it suitable for use in tropical areas for multice ntric studies. Such Studies could lead to a better knowledge of the natural history of the human disease. The method is also suitable for experimental evaluation of improved antibiotic treatments for leptospirosis. (C) 2001 F ederation of European Microbiological Societies. Published by Elsevier Scie nce B.V. All rights reserved.