The bacterial cause of syphilis was discovered in 1905. German zoologist Fritz Schaudinn and dermatologist Erich Hoffmann identified the spiral-shaped organism in tissue from patients with syphilis at the Charité clinic in Berlin.
They initially called it Spirochaeta pallida. It is now known as Treponema pallidum subspecies pallidum, a delicate spirochaete bacterium that causes the sexually transmitted form of syphilis. The organism’s extremely slender, coiled shape made it difficult to study with ordinary staining methods, so dark-field microscopy became especially important for viewing it.
The discovery clarified the cause of a disease that had long been known for its changing and sometimes misleading symptoms. Syphilis is often called “the great imitator” because it can resemble many other illnesses. The first effective drug treatment, Salvarsan, followed several years later, while penicillin became the standard highly effective treatment in the 20th century.