Discovery of the Cholera Bacterium

The bacterium that causes cholera was first observed under a microscope in 1849 by French zoologist Felix-Archimede Pouchet, who examined it in the stool of cholera patients but mistakenly identified it as a protist rather than a bacterium. Italian physician Filippo Pacini correctly identified the organism as a bacterium in 1854, describing comma-shaped bacilli in the intestinal tissue of cholera victims, though his work went largely unnoticed at the time. German physician Robert Koch, working independently, isolated the same organism in pure culture in Calcutta in January 1884 and established its role in causing the disease, publishing results that finally brought the bacterium, later named Vibrio cholerae, to wide scientific attention. John Snow's earlier 1854 epidemiological study of a London cholera outbreak had already shown that the disease spread through contaminated water rather than foul air, but it was Pacini's and Koch's bacteriological work that identified the actual organism responsible.