Written By:The Editors of Encyclopaedia Britannica
Alexandre Yersin, in full Alexandre-Émile-John Yersin, also called Alexandre-John-Émile Yersin (born Sept. 23, 1863, Lavaux, near Aubonne, Switz.—died March 1, 1943, Nha Trang, Annam, Indochina [now in Vietnam]) Swiss-born French bacteriologist and one of the discoverers of the bubonic plague bacillus, Pasteurella pestis, now called Yersinia pestis.
Yersin studied medicine at the universities of Marburg and Paris and bacteriology with Émile Roux in Paris and Robert Koch in Berlin. In 1888 he and Roux isolated a toxin secreted by the diphtheria bacillus (bacterium) and showed that the toxin—and not the microorganism—gives rise to the symptoms of the disease. … (100 of 298 words)