The History of Cholera - Robert Koch
Three decades later, unaware of the fact that Pacini had already done the same research at the University of Florence and had obtained significant results, Robert Koch, one of the “fathers" of microbiology and bacteriology, was also researching the microorganism causing cholera. In his quest for the cholera-causing bacterium, he traveled to Alexandria, in Egypt, where an epidemic of the disease was running rampant. Once in Egypt, he performed analyses on the bodies of the victims of the disease and he found a bacillus, the same one that Pacini had found, in the intestinal mucosa.
Koch was unsure, however, on whether the presence of this bacillus was the cause or the consequence of the disease and decided to find out by isolating the bacterium, growing a pure culture of it, infecting animals with the microorganisms and observing if the disease would develop. Even though he wasn’t able to create a pure culture of the bacteria, he infected animals with the bacteria he obtained; none of the animals contracted the disease.
Koch moved his research to India, which was another cholera “hotspot". There he and his team were able to grow the bacteria in a pure culture and, consequently, it was possible for them to perform more attentive observations and analyses. The first thing that Koch noticed was the bent shape of the bacillus, which made it look similar to a comma. Moreover, he saw that damp earth and moist soiled linen were the places where the bacteria would grow and proliferate, while they were highly vulnerable to drying and weak acid solutions.
Koch also observed that these organism were present in great quantity in the typical “rice water stool" in patients who were suffering from an advanced state of cholera, while they were never present in patients who suffered from diarrhea that resulted from other causes. Koch was never able to infect animals with the bacteria that he cultivated and his conclusion, which was correct, was that animals are immune to cholera.