Leptospira interrogans is a Gram negative, obligate aerobe spirochete, with periplasmic flagella. When viewed through a light microscope, it often resembles a question mark, and this gives the species its name. It is a member of the genus Leptospira. Some important pathogenic serovars from this species are Canicola, Icterohaemorrhagiae and Australis. L. interrogans is difficult to culture, requiring special media and extended incubation periods.