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The Impact Scientist on the Curious Case of Dr. Pettenkofer

Come back in time to the end of the 19th century. Science is becoming increasingly important in peoples’ daily lives and is altering the beliefs and traditions of centuries. Cogs and belts whirr and steel lurches to perform the work of 1000 horses. Cities have grown massively in the past 100 years since the industrial revolution, fueled by the application of science.

But something lurks in the shadows: there are dreadful killers abound. Coughs, wheezes and groans can be heard as people die slowly throughout the cities. Contagious diseases wrought havoc and destruction on the lives of people all over Europe, and science had a lot to answer for.

We now know that contagious diseases are caused by viruses and bacteria but, at the time, two ideas on the cause of the increase in disease were hotly debated: infection by organisms like bacteria and viruses (although viruses remained undiscovered until the 1930s), or infection by miasma, dirty air, which suggested that filth and dirt caused illness.

The miasma theory of infection had been widely accepted for many centuries – it made sense that things which look and smell bad cause illness, as opposed to unimaginably small living cells.

The two main players in this story are a Dr. Koch, well known for his work in microbiology, and the little known Dr. Pettenkofer. At the end of the 19th century, on the verge of an outbreak of cholera in Hamburg, Koch purported that a certain bacteria, Vibrio cholerae, was responsible for the diarrhea inducing infection. Meanwhile, Dr. Pettenkofer was convinced that the outbreak was due to the high levels of pollution in the city; cholera was spread via the atmosphere and was only contagious under certain conditions.

To prove his point, Pettenkofer planned a drastic experiment – he wrote to Koch and requested a sample of his newly identified bacteria, with the intention of drinking it. If Koch’s hypothesis was correct, Pettenkofer would surely come down with cholera – but this was not the case; Pettenkofer felt a little unwell but suffered no other effects. Satisfied, he thought he had disproved the germ theory of disease.

Germ theory has since been validated, however, and has formed the basis of modern medicine and microbiology. We now know cholera is caused by the bacteria Vibrio cholerae, and as few as 10 colony forming units (CFUs are the living and healthy bacteria) are capable of infecting a healthy person. Pettenkofer drank as many as a billion CFUs. The bacteria releases toxins which alter how cells hold on to water, causing severe diarrhea and life threatening dehydration. So the real question is – how did Pettenkofer come out with his trousers clean?

Allow me to put forward my own pet theory. Vibrio cholerae is highly infectious at low levels. However, once the level of bacteria builds up in an infected person, a change occurs in the biology of the bacteria. Instead of becoming more severe, Vibrio cholera turns off its virulence, shutting down its toxin production and swimming off down stream to infect another person. This process, known as quorum sensing, allows bacteria to communicate in order to decide how to act as a group. To our knowledge, most bacteria use these molecules to increase virulence. Vibrio cholerae works the other way around; it counts these votes and when a certain level is reached, the virulence is turned off.

This little biological trick may have been key to Pettenkofer’s survival. If the Vibrio cholerae he drank was at a high enough density, it may have just passed right through him. But, despite his radical experiment, Pettenkofer’s results were largely ignored. Koch, on the other hand, had just been consulted regarding a new water system for the city of Munich. Pettenkofer carried on working into old age until depression took over and he ended his life alone one evening. Koch went on to isolate the bacterium that causes TB, discover a way to isolate anthrax from blood samples and won the Nobel prize in 1905 for “his investigations and discoveries in relation to tuberculosis”.

Although Pettenkofer’s idea was wrong, I greatly admire his bravery. Even knowing in far greater detail than either man knew of bacteria in their days, I would never dream of drinking a vial of live Vibrio cholerae. Such self-experimentation has been repeated more recently by an Australian researcher. Dr. Marshall and his colleague had been looking into the cause of stomach ulcers, which is a leading cause of stomach cancer. Like Dr. Pettenkofer, Dr. Marshall also drank his newly identified bacterium H. pylori. Unlike Dr. Pettenkofer, Marshall did get ill and ended up with a stomach ulcer – as well as the Nobel Prize in 2005.

How different would Pettenkofer’s story be if things hadn’t gone his way? Pettenkofer’s principles of testing his ideas is the foundation on which Science progresses and, for this at least, he should be recognised.

James Gurney

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