Leptospirosis is caused by a bacteria of the genus Leptospira which includes a large number of species ; these have been regrouped into two entities :
Leptospira interroganssensu lato, which groups together at least 8 species pathogenic for a number of mammals including man : it comprises approximately 230 serovars and 23 serogroups. The serovar is the basic taxonomy of the class Leptospira.
Leptospira biflexa sensu lato, includes non pathogenic species and freshwater saphrophytes.
The diagnosis of Leptospirosis can be bacteriological and/or serological. In both cases, the diagnosis is based on phenotypic analyses established in 1918 by Martin and Pettit using an agglutination-lysis (RAL) test and which has evolved to become the microagglutination test or MAT. This remains the reference test. Because of the significant frequency of false positives and false negatives, a biological diagnosis is also essential to fully evaluate the endemic levels of leptospirosis
DNA analysis using gene amplification allows an early and rapid diagnosis of the disease. The serovar responsible can be determined following the isolation and subsequent identification of the strain. Generally speaking, serological data can give a diagnosis at the serogroup level : however, data interpretation must be taken into consideration and the methods used need to be normalised..
The peripheral laboratories (grade I) and the central laboratories (grade II) may carry out certain serological techniques. The National Reference Centre (grade III) provides them with reference
sera and with the culture media necessary for strain identification. These laboratories play a vital role in sample collection and in subsequent epidemiological and clinical analyses of each sample. They provide an essential link between the Reference Centre and the clinical services.
The serological test using MAT and a complete range of antigens can only be carried out by a reference laboratory because a stock of reference strains must be continually maintained. The same exigency is necessary for strain identification. The Leptospires Laboratory, Pasteur Institute, 75724 Paris Cedex 15 was designated the National Centre of Reference of Leptospires (NCRL).
In addition to its research, including improvements and advances in techniques, the NCRL gives technical advice and epidemiological information and helps to locate strains for interested laboratories. It also organises courses and carries out evaluations and surveys.
edited by Institut Pasteur.
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