Robert Koch

• 1. Introduction

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  Robert Koch announced the cause of tuberculosis before the German Physiological Society in Berlin on the 24th of March 1882. There was no particular reaction. Eminent scientists like Rudolf Virchow stayed skeptical, clinging to the idea that all disease came from faulty cells. Yet one listener, Paul Ehrlich, later called that moment his single greatest scientific experience. The man at the lectern was a German physician who had begun his real work in a private laboratory next to his patient examination room, with a microscope his wife had given him as a birthday gift. How does a district doctor in a small Prussian town become a person the Nobel Committee trusts to settle a dispute between nations? How does the same mind that helped found modern bacteriology also produce what is remembered as his greatest failure? Robert Koch lived from the 11th of December 1843 to the 27th of May 1910, and his story holds both.

• 2. The Anthrax Breakthrough

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  Near Wollstein, in Prussian Posen, anthrax was regularly killing humans and livestock, and no one could explain why. Koch had become district physician there in 1872, and he turned the puzzle into a research project. In 1876 he found that anthrax was triggered by one single pathogen, later named Bacillus anthracis. He uncovered the dormant stage, the anthrax spores, which could lie inactive under certain conditions and then activate to cause disease. To pin down the culprit, he dry-fixed bacterial cultures onto glass slides, stained them with dyes, and watched them under a microscope. This made him the first scientist to link a specific microorganism to a specific disease. He rejected the idea of spontaneous generation and supported the germ theory. He published the finding in 1876 in a booklet titled Die Atiologie der Milzbrand-Krankheit, written while still in Wollstein. His 1877 publication on the structure of the anthrax bacterium carried the first photograph of a bacterium. The work impressed Ferdinand Julius Cohn, professor at the University of Breslau, who helped him publish and invited him to demonstrate the new bacterium in 1877. All of it came from a poorly equipped laboratory, a detail that made the achievement only more striking.

• 3. Glass, Agar, And The Dish

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  Potato slices were Koch's first attempt at a solid place for bacteria to grow. On them he could see individual colonies of identical, pure cells, but the slices did not suit every organism. He turned to nutrient solutions with gelatin and hit a wall, because gelatin does not stay solid at 37 degrees Celsius, the ideal temperature for most human pathogens, and many bacteria simply liquefy it. The answer came through his post-doctoral assistant Walther Hesse, who got the idea from his wife Fanny Hesse. In 1881 Koch began using agar, a polysaccharide that stays solid at 37 degrees, resists most bacteria, and forms a stable transparent medium. Koch also reshaped microscopy itself. He was the first to use an oil immersion lens and a condenser to see smaller objects, and the first to use microphotography for observation. He introduced staining with methylene blue and Bismarck brown dye. His 1881 booklet Zur Untersuchung von pathogenen Organismen became known as the Bible of Bacteriology. In it he described pouring liquid agar onto a glass slide, spreading gelatin over it, and sealing the culture in a moist chamber he called the feuchte Kammer. The typical chamber was a circular glass dish 20 centimeters across and 5 centimeters high, with a lid against contamination. He demonstrated the plating method at the Seventh International Medical Congress in London in August 1881, where Louis Pasteur exclaimed, C'est un grand progres, Monsieur. His assistant Julius Richard Petri later published a minor modification in 1887, using the circular dish directly as the main container, and the world gave it Petri's name rather than Koch's.

• 4. The Bacillus Beneath Tuberculosis

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  In the 1880s, while serving as government advisor with the Imperial Health Agency in Berlin, Koch grew convinced that tuberculosis was not inherited but caused by a bacterium and spread by infection. In 1882 he reported the agent to be the slow-growing Mycobacterium tuberculosis. He described how cover-glasses left in a staining fluid of methylene blue mixed with potassium hydroxide for 24 hours revealed very fine rod-like forms in the tubercular mass, which multiplied and formed spores like the anthrax bacillus. The blue-stained tubercle bacilli, he noted, kept their beautiful blue color while the surrounding material turned brown. He expanded the work into a booklet in 1884 titled Die Atiologie der Tuberkulose, concluding that the bacilli do not merely accompany tuberculosis but cause it. He called them the true agents of tuberculosis. The discovery later anchored Koch's postulates, the principles for tying a pathogen to a disease, formulated by his assistant Friedrich Loeffler in 1883. The day of the announcement, the 24th of March, has been marked by the World Health Organization as World Tuberculosis Day every year since 1982.

• 5. The Tuberculin Disaster

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  By February 1890, Koch's notebook shows he had tested hundreds of compounds in search of a tuberculosis cure. He found that an extract from the tuberculosis bacterium culture, dissolved in glycerine, could cure the disease in guinea pigs. Experiments from April to July 1891 led him to conclude the extract did not kill the bacterium but destroyed infected tissue by necrosis, starving the bacteria. He made a vague announcement in August 1890 at the Tenth International Medical Congress in Berlin, describing a substance that halted the tuberculous process. In November 1890 he showed its effect in humans, delivering it through shallow skin punctures, and patients and doctors flocked to Berlin for his remedy. He kept the source secret for nearly a year. The trials turned disastrous. Rudolf Virchow's autopsy report on 21 treated subjects, given to the Berlin Medical Society on the 7th of January 1891, found that the patients died because of the treatment rather than being healed. Koch then admitted the drug was a glycerine extract of cultivated tuberculosis bacilli. The first clinical trial report in 1891 covered 1061 patients with internal tuberculosis and 708 with external tuberculosis, and the German official report late that year declared the disease was not cured. His secrecy, it emerged, sprang from ambition for monetary benefit and for an institute of his own. The fallout cost him dearly. He was released from the University of Berlin and made director of the newly established Royal Prussian Institute for Infectious Diseases in 1891, forbidden from working on tuberculin or claiming patents on his later work. His name survived in the field through Koch's phenomenon, the extreme skin reaction seen at the vaccination site in someone already infected. The substance itself is now used to test for hypersensitivity in tuberculosis patients.

• 6. Cholera On The Ganges

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  In August 1883 the German government sent a medical team under Koch to Alexandria, Egypt, to investigate a cholera epidemic. He found bacterial infection in the intestinal mucosa of everyone who died, but could not yet confirm the bacteria were the cause. As the Egyptian outbreak faded, he moved to Calcutta, India, where the epidemic was worse. He found the river Ganges to be the source, performed autopsies on almost 100 bodies, and found infection in each. He isolated the bacterium in pure culture on the 7th of January 1884 and described it as a little bent, like a comma. Fresh blood samples showed the bacterium could kill red blood cells, and he proposed it used some kind of poison; that poison, the cholera toxin, was discovered in 1959 by the Indian scientist Sambhu Nath De. Koch could not fully satisfy his own postulates, because his pure culture did not produce disease in animals, which he correctly explained were immune to human pathogens. The comma bacillus had in fact been described earlier, by the Italian physician Filippo Pacini in 1854 and observed around the same time by the Catalan physician Joaquim Balcells i Pascual, though neither tied it to cholera. Koch's colleague Richard Friedrich Johannes Pfeiffer renamed it Vibrio cholera in 1896.

• 7. A Mind For Combat

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  Koch and Pasteur were friendly at their first meeting in London in August 1881, but the rest of their careers ran on dispute. The trouble began with how Koch read his 1876 anthrax discovery, treating the germ as the proven cause when, by his own later standards, it was an inference. Pasteur argued that his 1881 anthrax vaccine, not Koch's claim, was the full proof of causality. Koch had written that anthrax never occurs without viable anthrax bacilli or spores, and that a Pasteur-style vaccine would be impossible. Pasteur sent his assistant Louis Thuillier to Germany to demonstrate the vaccine and disprove the point. At the International Congress for Hygiene in Geneva in 1882, Koch called Pasteur's methods unreliable and said they inevitably lead to false conclusions. He later said Pasteur is not a physician, and one cannot expect him to make sound judgments about pathological processes. Koch's combativeness shaped science even when he was not the discoverer. The Nobel Committee chose the 1902 prize to honor the transmission of malaria but could not decide between the British surgeon Ronald Ross and the Italian biologist Giovanni Battista Grassi. Koch was appointed neutral arbitrator. Grassi had criticized his malaria research in 1898, while Ross had kept a cordial relationship. Koch threw the full weight of his authority into insisting Grassi did not deserve the honor, and Ross took the award. On the question of cattle tuberculosis, Koch reversed himself more than once, finally telling the Third International Congress on Tuberculosis in London in July 1901 that bovine tuberculosis posed no danger to humans, prompting the chair, Joseph Lister, to reprimand him with the medical evidence.

• 8. After Wollstein

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  Emperor Wilhelm I awarded Koch the Order of the Crown, 100,000 marks, and appointment as Privy Imperial Councillor. He was made a Knight Grand Cross in the Prussian Order of the Red Eagle on the 19th of November 1890 and elected a Foreign Member of the Royal Society in 1897. In 1905 he received the Nobel Prize in Physiology or Medicine for his investigations and discoveries in relation to tuberculosis. The Robert Koch Medal, established to honor the greatest living physicians, came in 1908. His curiosity never settled in Berlin. In 1906 he moved to East Africa to seek a cure for sleeping sickness, setting up the Bugula research camp where up to 1000 people a day were treated with the experimental drug Atoxyl. Earlier, on the 26th of December 1900, he had reached German New Guinea and noticed that the Papuan people carried malaria parasites yet suffered only mild or unnoticed bouts, while German settlers and Chinese workers fell sick at once and grew resistant only over time, an early observation of acquired immunity. His private life moved alongside the work. He married Emma Adolfine Josephine Fraatz in July 1867 and had a daughter, Gertrude, in 1868; the marriage ended after 26 years in 1893, the same year he married the actress Hedwig Freiberg. On the 9th of April 1910 he suffered a heart attack and never fully recovered. Three days after lecturing on his tuberculosis research at the Prussian Academy of Sciences, he died in Baden-Baden on the 27th of May 1910, at the age of 66. The institute he founded was renamed in his honor, and on the 10th of December 2017, the eve of his birthday, a Google Doodle marked the man who first photographed a bacterium.