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Cholera is an infectious, at times deadly disease that is caused by a bacterium called Vibrio cholerae. The main culprit behind several pandemics that devastated Europe in the past centuries, cholera is characterized by an infection of the intestine by colonies of the bacteria, from which a potent toxin is produced. This toxin causes body fluids to be lost along the inside layer of the intestine; very watery diarrhea results. If the patient is not promptly treated, death by dehydration can occur in only a couple of hours.
One of the most common mistakes that people are prone to making when talking about who first isolated the bacterium causing cholera is believing that we owe this discovery to the prominent German scientist, Robert Koch. So who discovered cholera? While it is true that the fame and the credit for the discovery went to Koch for many years, the first scientist who identified the bacterium causing the disease was Italian scientist Filippo Pacini, thirty years before Koch.
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The History of Cholera - Filippo Pacini
Before the study of bacteria gained importance and before microorganisms were linked to infectious diseases (in other words, before the germ theory of disease), it was believed that cholera was caused by an excessive production of bile by the patient; in fact, the word choler in Greek means bile. In the 1800s, however, as new scientific instruments and tools were being created, new observations were being made, and new theories were taking hold, this explanation was no longer satisfactory, and scientists started to look for new answers.
In the middle of the 19th century, around the time a cholera pandemic was devastating Asia, the disease arrived in Italy. Adamant about discovering the basis for the onset and the transmission methods of cholera, Pacini started performing autopsies on the bodies of victims. Specifically, he did several histological analyses on the mucosa, or the inner layer of their intestines and observed samples under the microscope. These tests and observations led Pacini to the isolation of a comma-shaped bacillus, which he called Vibrio. Pacini’s results were first published in 1854 in a paper whose title was “Microscopic observation and pathological deductions on cholera", but for years and years the existence and importance of this paper were unknown.
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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.
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The observations and discoveries that Koch performed led him to become a hero in the field and for years, he was given complete credit for the discovery and isolation of Vibrio cholerae. In 1965, however, 82 years after his death, the International Committee on nomenclature decided to officially name the organism which causes cholera Vibrio Cholerae Pacini 1854, to honor the fact that Pacini was the first one to ever isolate and identify the bacillus.