Transmission and treatment of tuberculosis
Over his incredible career Robert Koch made many discoveries, but received his Nobel Prize for contributions to understanding the causes of tuberculosis. He was the first person to show that bacteria caused infectious disease. He provided a methodology for showing whether a parasitic organism was responsible for a disease. This involved staining the parasitic organism in infected tissue and isolating it into a pure culture. An experimental animal was then inoculated with this culture, and he observed whether it showed symptoms of the disease. With this method he demonstrated both that tuberculosis was infectious, and that it was caused by the bacteria Tubercle Bacillus.
Kochs work on the bacteria shed a light on many aspects of tuberculosis. He showed that the bacillus was dependant on its host organism for development, and that the disease was primarily spread through the phlegm of consumptives. This meant it could be controlled through care of the sick and good hygiene.
He developed a means of diagnosing tuberculosis in its early or dormant stages, which helped to control transmission of the disease.
He also showed that tuberculosis in humans and cattle were caused by different bacteria. Demonstrating the effect of the isolated bacteria on animals, to show which ones caused a disease allowed scientists to identify organisms responsible for many other diseases. This was a major step forward for medicine.