Bacteriologist Shibasaburo Kitasato made several important contributions to the understanding of human disease and how the body fights off infection. He also discovered the bacterium that causes bubonic plague.

Born in Kumamoto, Japan, Kitasato, completed his medical studies at the University of Tokyo in 1883. Shortly after, he traveled to Berlin to work in the laboratory of Robert Koch. Among his greatest accomplishments, Kitasato discovered a way of growing a pure culture of tetanus bacillus using anaerobic methods in 1889. In the following year, Kitasato and German microbiologist Emil von Behring reported on the discovery of tetanus and diphtheria antitoxin. They found that animals injected with the microbes that cause tetanus or diphtheria produced substances in their blood, called antitoxins, which neutralized the toxins produced by the microbes. Furthermore, these antitoxins could be injected into healthy animals, providing them with immunity to the microbes. This was a major finding in explaining the workings of the immune system. Kitasato went on to discover anthrax antitoxin as well.

In 1892, Kitasato returned to Tokyo and founded his own laboratory. Seven years later, the laboratory was taken over by the Japanese government, and Kitasato was appointed its director. When the laboratory was consolidated with the University of Tokyo, however, Kitasato resigned and founded the Kitasato Institute.

During an outbreak of the bubonic plague in Hong Kong in 1894, Kitasato was sent by the Japanese government to research the disease. He isolated the bacterium that caused the plague. (Alexandre Yersin, 1863 - 1943, independently announced the discovery of the organism at the same time). Four years later, Kitasato and his student Kigoshi Shiga were able to isolate and describe the organism that caused one form of dysentery.

Kitasato was named the first president of the Japanese Medical Association in 1923, and was made a baron by the Emperor in 1924. He died in Japan in 1931.