on bacteriology and immunology that were widely popular, even after his death in 1957. Discovery of Shigella dysenteriae After graduating the Tokyo Imperial University school of medicine, Kiyoshi Shiga began his career as an assistant to Kitasato Shibasaburō at the Institute for the Study of Infectious Diseases. While studying many infamous diseases at the time, Kitasato and his colleagues, including Shiga, turned their focus to discovering the microorganism that caused the dysentery outbreak in 1897. In 1898, Shiga was able to isolate and identify the microorganism causing the infectious disease by studying patients who had dysentery and following Koch's Postulates. Using gram staining methods, Shiga was able to further deduce that the microorganism causing dysentery was a gram-negative bacillus. Kiyoshi Shiga initially called the bacteria Bacillus dysenteriae, but the name was later changed to Shigella dysenteriae as a tribute to Kiyoshi Shiga. The discovery of the gram-negative bacillus led to the identification of other species of bacteria with similar characteristic. These species of bacteria are classified under the Shigella genus. Species of Shigella are further separated by serogroups that represent different serotypes. Through further studies of the S. dysenteriae bacteria, Shiga was able to discover the Shiga toxin that is produced by the organism. With this new discovery, Shiga attempted to make a vaccine from the toxin. He tested his first attempt, a heat-killed S. dysenteriae strain vaccine, on himself which proved to be ineffective and caused severe complications. Kiyoshi Shiga continued his efforts and created a passive immunization vaccine that was based on horse serum. Test trials for the passive immunization vaccine showed no beneficial results or immunity to the infection. These setbacks led Shiga to stop any further trials or production of a Shiga toxin-based vaccine. Research Shiga had done research on other topics aside from Shigella dysenteriae including tuberculosis, leprosy, and beriberi throughout his career and grew an interest in chemotherapy and immunology. After the Shigella dysenteriae discovery, Kiyoshi Shiga worked with Paul Ehrlich in Europe on discovering chemotherapy methods for a blood diseases called trypanosomiasis which was caused by a protozoan microorganism. Paul Ehrlich is known for his work with dyes and their ability to distinguish and kill certain bacteria and tissues. Ehrlich's previous research, before working with Shiga, lead to the discovery of chemotherapy. Shiga and Ehrlich's research into chemotherapy dyes lead them to the discovery of trypan red, a drug that was proven to