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 Sanità, Rome) was established in 1956 by B. Babudieri, efforts have been devoted to identifying new Leptospira isolates and maintaining a collection of strains that today comprises 670 strains, 550 of which have been totally or partially classified, and 120 are still under study. This collection includes 23 serogroups and 156 serovars of pathogenic leptospires, and 32 serogroups and 54 serovars of saprophytic leptospires. The conventional serogroup and serovar identification, mainly based on antigenic relatedness, is tedious and time-consuming, requiring the maintenance of a comprehensive collection of serovar reference strains and the preparation of the corresponding rabbit antisera. Although considerable difficulties are encountered in the classification of leptospires at the serogroup and serovar level, this classification system is essential to obtain information on the epidemiology of leptospirosis in the different geographical areas. Serovar identification has become faster with the introduction of pulsed-field gel electrophoresis (PFGE) of large DNA fragments obtained after digestion of leptospiral DNAs with rare-cutting restriction enzymes. This technique has been successfully utilized to discriminate between closely related serovars of the Leptospira interrogans complex. We have recently used PFGE to characterize several Italian leptospiral isolates, confirming that PFGE analysis combined with microscopic agglutination test (MAT) with monoclonal and polyclonal antibodies can be used as an accurate and reliable method to compare and classify leptospires.