Leptospira strains kept at the National Centre for Leptospirosis in Rome, Italy

Since the National Centre for Leptospirosis (Department of Bacteriology and Medical Mycology, Istituto Superiore di Sanita, Rome) was established in 1 956 by B. Babudieri, efforts have been devoted to identifying new Leptospir a isolates and maintaining a collection of strains that today comprises 670 strains, 550 of which have been totally or partially classified, and 120 a re still under study. This collection includes 23 serogroups and 156 serova rs of pathogenic leptospires, and 32 serogroups and 54 serovars of saprophy tic leptospires. The conventional serogroup and serovar identification, mai nly based on antigenic relatedness, is tedious and time-consuming, requirin g the maintenance of a comprehensive collection of serovar reference strain s and the preparation of the corresponding rabbit antisera. Although consid erable difficulties are encountered in the classification of leptospires at the serogroup and serovar level, this classification system is essential t o obtain information on the epidemiology of leptospirosis in the different, geographical areas. Serovar identification has become faster with the intro duction of pulsed-field gel electrophoresis (PFGE) of large DNA fragments o btained after digestion of leptospiral DNAs with rare-cutting restriction e nzymes. This technique has been successfully utilized to discriminate betwe en closely related serovars of the Leptospira interrogans complex. We have recently used PFGE to characterize several Italian leptospiral isolates, co nfirming that PFGE analysis combined with microscopic agglutination test (M AT) with monoclonal and polyclonal antibodies can be used as an accurate an d reliable method to compare and classify leptospires.