Adaptation of a real-time PCR method for the detection and quantification of pathogenic leptospires in environmental water.

Leptospirosis is a major zoonotic disease that affects humans and animals in all continents, in both rural and urban areas. In Europe, metropolitan France is the most affected country, with about 300 human cases declared per year. In France, although leptospirosis is now mostly considered as a recreational disease related to freshwater areas, isolation of pathogenic leptospires from environmental water samples still remains difficult. It thus seemed important to set up an efficient method to detect and quantify these bacteria in this environment. We determined a DNA extraction method suitable for freshwater samples and adapted a real-time quantitative PCR based on the detection of the LipL32 gene using the SYBR green chemistry. The method developed is specific for pathogenic Leptospira. It permits the detection of all the pathogenic strains tested and none of the saprophytic strains. Quantification is possible between 10 and 10(7) bacteria/mL, and therefore, the method represents a tool that could be integrated into future public health surveillance programs for recreational freshwater areas.