Kitasato was born in Okuni village, Higo Province,. He was educated at Kumamoto Medical School and Tokyo Imperial University. He studied under Robert Koch in the University of Berlin from 1885 to 1891. In 1889, he became the first person to grow the tetanus bacillus in pure culture, and in 1890 cooperated with Emil von Behring in developing a serum therapy for tetanus using this pure culture. He also worked on antitoxins for diphtheria and anthrax. Kitasato and Behring demonstrated the value of antitoxin in preventing disease by causing passive immunity to tetanus in an animal that received graded injections of blood serum from another animal infected with the disease. After returning to Japan in 1891, he founded the Institute for Study of Infectious Diseases with the assistance of Fukuzawa Yukichi. One of his early assistants was August von Wassermann. Kitasato demonstrated how dead cultures can be used in vaccination. He also studied the mode of infection in tuberculosis. He traveled to Hong Kong in 1894 at the request of the Japanese government during an outbreak of the bubonic plague, and identified a bacterium that he concluded was causing the disease. Yersin, working separately, found the same organism several days later. Because Kitasato's initial reports were vague and somewhat contradictory, some scientific historians give Yersin sole credit for the discovery; while others advise dual credit. However, a thorough analysis of the morphology of the organism discovered by Kitasato by microbiologists determined that although his samples likely became contaminated later, leading to the conflicting reports from his laboratory, there is "little doubt that Kitasato did isolate, study, and reasonably characterize the plague bacillus" in Hong Kong and "should not be denied this credit". Four years later, Kitasato and his student Shiga Kiyoshi were able to isolate and describe the organism that caused dysentery. When the Institute for Infectious Diseases was incorporated into TokyoImperial University in 1914, he resigned in protest and founded the Kitasato Institute, which he headed for the rest of his life. In September 1921, Kitasato founded, together with several medical scientists, the Sekisen Ken-onki Corporation, with the intention of manufacturing the most reliable clinical thermometer possible. The company was later renamed Terumo Corporation. Kitasato also was the first dean of medicine at Keio University, first president of the Japan Medical Association, and served on the House of Peers. He was ennobled with the title of danshaku in the kazoku peerage system in February 1924. Kitasato Shibasaburō died of an intracranial hemorrhage at his home in Azabu, Tokyo, on June 13, 1931. His grave is at the Aoyama Cemetery in Tokyo.
