The French connection between Louis Pasteur and Joseph Lister’s eureka moment that lead to victory over infection.

Our Senior Research Fellow, Professor Ken Donaldson, looks at how Joseph Lister was inspired by Louis Pasteur’s swan neck flasks.

By the nineteenth century the origins of living things had become the interest of scientists, with many rejecting the old belief that life could develop from non-living matter – the so called ‘spontaneous generation’ of life. For example, it had been believed that to make mice you need only put some rags mixed with old bread and cheese in a dark corner and after a few days, ‘hey presto’ – mice were generated! Maggots suddenly appearing in putrefying meat and fish was another case of spontaneous generation of living things that had challenged scientists since the 17th century.  This was solved using mesh to cover the meat and observing that, as long as the size of the mesh excluded flies, then no maggots arose in the meat. However, meat still putrefied even if the flies were excluded and no mesh was fine enough to exclude whatever was causing the putrefaction. Whilst this was annoying it wasn’t until large scale problems of wine spoilage during fermentation, in the French wine industry, began to occur that the French government woke up to the problem. They asked Louis Pasteur the brilliant French chemist and ‘Father of microbiology’ to address the problem. His experiments concluded that microscopic organisms omnipresent in the air – yeast – normally fermented the wine to make alcohol, but that other tiny organism in the air could spoil the wine if they grew, displacing the yeasts.

Portrait of Louis Pasteur. Paul Nadar, Public domain, via Wikimedia Commons

From his experiences with wine spoilage and putrefaction, Pasteur began to believe that air, water and the environment in general were teeming with micro-organisms and that these were the cause of meat putrefaction as well as spoiled fermentation in brewing. To prove the ubiquitousness of micro-organisms in the air, Pasteur developed the ‘swan-neck flask’  (col de cygnet in French) experiment. A liquid medium that encouraged the growth of micro-organisms was placed in a specially made glass ‘swan-neck’ flask, designed so that the medium was open but only to air through the long neck. As Pasteur predicted, the medium did not become contaminated because the although organisms abounded in the air, they could not reach the medium along the ‘swan neck’. Breaking the neck near the medium, as in the diagram, allowed the airborne microbes access since they have a short way to go, and the medium quickly became infected with microbes, turning it brown.

                            A diagram of Pasteur’s swan neck flask experiment.

In a brilliant leap of thinking, Pasteur realised that, while these organisms in air were mostly harmless to people, some might enter wounds in the human body causing putrefaction, pus and death. Scientists elsewhere were thinking vaguely along these lines but Pasteur, incidentally a chemist and not a medical doctor, realised the true importance of this idea, which became the ’germ theory‘ of disease.

One person who was most decidedly thinking about infection and working amongst it was the surgeon Joseph Lister in Glasgow. Every day he faced the reality of patients dying, not from their primary disease, but from ‘fever’ that developed following the surgery that was supposed to cure them. Their post-operative wounds became swollen and accumulated pus, releasing a nauseating smell and eventually taking the life of the patient.  Lister spent a long time thinking about and experimenting on tissue from such wounds and puzzling over how the pathological change arose. The current thinking was that a gas of some sort, called ‘miasma’, came from the wounds themselves and concentrated in them leading to tissue damage and pus formation, but Lister was not convinced of this.

Joseph Lister, Unknown author, Public domain, via Wikimedia Commons

Luckily in 1864, Thomas Anderson, the Professor of Chemistry in Glasgow, pointed Lister towards the work of Pasteur, particularly the swan neck flask experiment, which had been published in French journals in 1861. A light-bulb came on in Lister’s head and he realised that Pasteur’s swan-neck flask experiment demonstrated that microbes were ubiquitous in air and could readily enter open wounds during an operation. He also saw (and smelled) that the wound infection process could be analogous to putrefaction.

Lister puzzled over what to do to combat these microbes that he was now convinced abounded in the air. He had heard that creosote, a product of wood distillation (that was predominantly carbolic acid) was able to stop the putrefactive smell of sewage before it was spread in the fields. He later wrote

 “In the course of the year 1864 I was much struck with an account of the remarkable effects by carbolic acid upon the sewage of the town of Carlisle-preventing all odour from the lands irrigated with the refuse material”

So Lister plumped for dilute carbolic acid as something that might kill the microbes and counter infection. Because Pasteur had shown that the microbes were in the air it occurred to Lister to treat the air and so he developed a spray system that would produce a mist of carbolic acid over the site of the operation.  This greatly decreased post-operative wound infection and began the revolution in antisepsis that has saved countless lives since and made Lister a hero because of his pioneering work in combating infection.

An operation being performed using Lister’s carbolic acid spray. Unknown author Public domain, via Wikimedia Commons

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