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The Life of Sir Alexander Fleming
Chapter IX - The Mould Juice


God took care to hide that country till He judged His people ready-Then He chose me for His whisper and I've found it, and it's yours.

rudyard kipling

In most of the great scientific discoveries there has been one part deliberate research and one part luck, Pasteur, a man of unusual firmness of purpose who sought the truth with a combination of pure reason and experiment, was sometimes helped by Chance. He was called upon to deal with ad hoc problems which later were to lead him to general conclusions. If he had not been appointed to a professorship at Lille, if the distillers and brewers of the neighbourhood had not gone to him for advice, he might perhaps not have come to take an interest in fermentations, though, his genius being what it was, he would have discovered something else. Fleming had for a long time been hunting for a substance which should be able to kill the pathogenic microbes without damage to the patient's cells. Pure chance deposited this substance on his bench. But, had he not been waiting for fifteen years, he would not have recognized the unknown visitor for what it was. H

Once again, as at the very beginning of his career, he had just been taking stock of the weapons which medicine could employ against the infections. The means of defence were woefully inadequate, but he refused to give up hope. 'At present', he wrote, 'there seems little chance of finding any general antiseptic capable of killing bacteria in the blood stream, though there is some hope that chemicals may be produced with special affinities for special bacteria which may be able to destroy these in the blood, although they may be quite without action on other and, it may be, closely allied bacteria.'

He was studying a new antiseptic, mercuric chloride, which killed streptococci, though, as always, at a degree of concentration which the human body could not tolerate. He put the question to himself whether, by injecting it into the blood stream in weaker doses, it might not be possible to achieve a degree of concentration which would not destroy either the human cells or the streptococci, but might have the effect of making the latter more fragile and, consequently, more vulnerable to the action of the phagocytes.

His laboratory was still small and encumbered. An accumulation of culture dishes was piled in apparent disorder, though he could always find the one he wanted without a moment's hesitation. His door was almost always left open and any young research-worker in need of some variety of microbe or of some particular implement was given a warm welcome. Fleming would stretch out an arm, lay his hand at once on the required culture, give it to the intruder, and then, usually without uttering a word, go back to his work. When the air in the tiny room became stifling he would open the window which looked on to Praed Street.

In 1928 he agreed to contribute an article on the staphylococci to a vast undertaking — A System of Bacteriology — to be published by the Medical Research Council. Some time before this, his colleague, Merlin Pryce (now Professor Pryce) had, while working with him, devoted a certain amount of study to some abnormal forms, mutants, of these microbes.

Fleming, who liked nothing better than to give a helping hand to the young, wanted to quote Pryce in his article. But the latter had left Wright's department before he could complete his researches. Being a conscientious scientist he did not want to publish his results without verifying them, and his new job gave him insufficient leisure in which to do this quickly. Fleming, therefore, had to work again over the ground already covered by Pryce, and set himself to study numerous colonies of staphylococci. In order to examine these colonies, cultivated on agar in Petri dishes, he had to lift the lids of the dishes and leave the contents for some considerable time exposed under the microscope, which meant running a risk of contamination.

Pryce went to see Fleming in his little laboratory, where he found him, as usual, surrounded by innumerable dishes. The cautious Scot disliked being separated from his cultures before he was quite certain that there was no longer anything to be learned from them. He was often teased about his disorderly habits.

He was now to prove that disorder may have its uses. With his rough humour he reproached Pryce for obliging him to re-do a long job of work, and, while speaking, took up several old cultures and removed the lids. Several of the cultures had been contaminated with mould — a not unusual occurrence. 'As soon as you uncover a culture dish something tiresome is sure to happen. Things fall out of the air.' Suddenly, he stopped talking, then, after a moment's observation, said, in his usual unconcerned tones: 'That's funny On the culture at which he was looking there was a growth of mould, as on several of the others, but on this particular one, all round the mould, the colonies of staphylococci had been dissolved and, instead of forming opaque yellow masses, looked like drops of dew.

Pryce had often seen old microbial colonies which for various reasons had dissolved. He thought that probably the mould was producing acids which were harmful to the staphylococci — no unusual occurrence. But, noticing the keen interest with which Fleming was examining the phenomenon, he said: 'That's how you discovered lysozyme.' Fleming made no answer. He was busy taking a little piece of the mould with his scalpel, and putting it in a tube of broth. Then he picked off a scrap measuring about one square millimetre, which floated on the surface of the broth. He obviously wanted to make quite sure that this mysterious mould would be preserved.

'What struck me', Pryce says, cwas that he didn't confine himself to observing, but took action at once. Lots of people observe a phenomenon, feeling that it may be important, but they don't get beyond being surprised — after which, they forget. That was never the case with Fleming. I remember another incident, also from the time when I was working with him. One of my cultures had not been successful, and he told me to be sure of getting everything possible out of my mistakes. That was characteristic of his whole attitude to life.'

Fleming put the Petri dish aside. He was to keep it as a precious treasure for the rest of his life. He showed it to one of his colleagues: 'Take a look at that,' he said, 'it's interesting — the kind of thing I like; it may well turn out to be important.' The colleague in question looked at the dish, then handed it back with a polite: 'Yes, very interesting.' But Fleming, in no way discouraged by this manifestation of indifference, temporarily abandoned his investigation of the staphylococci, and gave himself entirely to studying the surprising mould.

What exactly is a mould? It is one of those tiny fungi, green, brown, yellow or black, which proliferate in damp cupboards or on old boots. This type of vegetation results from 'spores' — smaller than a red blood corpuscle — reproductive organs which float in the air. When one of them settles upon a suitable medium, it germinates, buds and puts out shoots in every direction until a soft mass forms.

Fleming transferred several spores to a dish containing agar and left them for four or five days to germinate at room temperature. He soon obtained a colony of the mould similar to the first one. Then he planted in the same agar different bacteria in isolated streaks, forming, as it were, the radii of a circle with the mould as centre. After incubation, he noticed that certain microbes survived in close proximity to the fungus — the streptococci, the staphylococci and the diphtheria bacillus, for instance, whereas the typhoid and influenza bacilli were not affected in the same way.

The discovery was becoming tremendously interesting. Unlike lysozyme, which acted more especially upon the inoffensive microbes, this mould seemed to produce a substance which could inhibit the growth of microbes which caused some of the most serious diseases. It might, therefore, have an immense therapeutic value. 'Here,' said Fleming, 'it looks as though we have got a mould that can do something useful.' He cultivated his penicillium in a larger receptacle containing a nutritive broth. A thick, soft, pock-marked mass, at first white, then green, then black, covered the surface. At first the broth remained clear. After several days, the liquid assumed a vivid yellow colour. What mattered now was to find out whether this liquid also possessed the bactericidal properties of the mould.

The methods perfected in 1922 for lysozyme suited Fleming's purpose admirably. He hollowed out a gutter in a dish of agar, and filled it with a mixture of agar and the yellow liquid. Then microbes were planted in streaks, perpendicularly to the gutter, up to the very edge of the dish. The liquid appeared to be just as active as the original mould. The same microbes were affected. There was therefore in the broth a bactericidal (or bacteriostatic) substance produced by the mould. How great a strength did it have? Fleming experimented with weaker and weaker solutions.— a 20th, a 40th, a 200th, a 500th. Even this last still arrested the development of the staphylococci. The mysterious substance contained in the golden liquid appeared to be endowed with quite extraordinary power. Fleming at that time had no means of knowing that the proportion of the active substance in the 'juice' was scarcely more than one in a million. The proportion of gold in the sea is greater than that.

It was important now to identify the mould. There are thousands of moulds. Fleming's knowledge of mycology (the science of fungi) was no more than elementary. He turned to his books, rummaged about in them, and decided that the substance in question was a penicillium of the genus chrysogenum. There happened just then to be at St Mary's a young Irish mycologist, C. J. La Touche, who was assisting Freeman in his researches into asthma. Freeman had got hold of him because a Dutch research-worker had put forward the theory that many cases of asthma among those living in damp rooms were due to moulds. La Touche was a sensitive individual who found the restless atmosphere of the Inoculation Department little to his liking. But he had made his colleagues aware of the importance of moulds, and they had affectionately nicknamed him 'Old Mouldy'.

Fleming showed his fungus to La Touche who, after studying it, decided that it was the penicillium rubrum. The bacteriologist deferred to the expert and in his first paper on the subject gave to his mould the name prescribed by La Touche. Two years later, the famous American mycologist, Thom, identified the fungus as a penicillium notatum (close to the chrysogenum which had been Fleming's first diagnosis). La Touche very graciously wrote to Fleming, apologizing for having misled him. Fleming learned from Thorn's book that the penicillium notatum had been originally recognized by a Swedish chemist, Westling, on a specimen of decayed hyssop. This reminded Fleming the Covenanter, of Psalm 51: 'Purge me with hyssop and I shall be clean' — the first known reference to penicillin.

Meanwhile, his experiments on the bactericidal action of the liquid had convinced him that he was in the presence of a phenomenon of antibiosis. The mould, a rudimentary living creature, produced a substance which killed other living creatures, microbes. The peaceful co-existence of the two species was not possible.

That living creatures could be caught up in a vital and murderous struggle, the spectacle presented by the world had always proved. They squabble over food, air and living-space. Sometimes they complement each other, the one providing what the other lacks, and, when that happens, a shared life, a 'symbiosis5 is possible. More often, however, proximity is fatal to one of them. In 1889 the Frenchman, Vuillemin, had for the first time employed the word 'antibiosis5, defining it thus: 'When two living bodies are closely united, and one of the two exercises a destructive action on a more or less extensive portion of the other, then we can say that "antibiosis" exists.'

A striking example is that of all the infectious microbes which are ceaselessly being emptied into water and soil. Most of them do not survive, and this must needs be so, since, otherwise, neither men nor animals could live at all. What is it that destroys these microbes? To a very great extent, the sun, but also the action of other microbes which are inoffensive, or even beneficial, to human beings. There are ancient Greek texts which point out that certain epidemics cause the disappearance of other ailments.

In Lister's Commonplace-Books (now in the library of the Royal College of Surgeons), we find under the date November 25th, 1871, the following observation: in a glass tube containing urine, Lister noticed the presence of numerous bacteria, but also of some granular filaments which he recognized as mould. Seeing that the bacteria seemed to be in poor condition, he made several experiments for the purpose of determining whether the growth of mould had the effect of making the liquid an unfavourable medium for bacteria. These experiments were inconclusive and he abandoned them. But he had noted that the presence of a soft mass (which he thought was penicillium glaucum) on the surface of the tube 'was making the bacteria completely immobile and languid'.

He supposed that what was happening was a competitive struggle for oxygen, the, penicillium absorbing that contained in the broth and blocking the surface.

In 1877, Pasteur and Joubert had noticed that the anthrax bacillus, when injected at the same time as inoffensive bacteria, produces no infection of the animal. There, again, an antagonism is set up, and the anthrax bacillus is vanquished. cIn the inferior organisms,' Pasteur wrote, 'still more than in the great animal and vegetable species, life hinders life. A liquid invaded by an organized ferment, or by an aerobe, makes it difficult for an inferior organism to multiply...' Farther on, having pointed out that a common bacterium introduced into urine at the same time as the bacterium of anthrax prevents the development of the latter, he adds: It is a remarkable thing that this same phenomenon occurs in the bodies of those animals which are most prone to contract anthrax, and we are led to the surprising conclusion that one can introduce a profusion of the anthrax bacterium into an animal without the latter contracting the disease; all that is needed is to add common bacteria to the liquid which holds the bacterium of anthrax in suspension. These facts may, perhaps, justify the greatest hopes from the therapeutic point of view.'1

In 1897, Dr Duchesne, of Lyon, gave to his thesis (inspired by Professor Gabriel Roux) the title: Contribution d Vetude de la concurrence vitale chez les micro-organismes. Antagonisme entre les moisissures et les microbes. Tt is to be hoped', he concluded, cthat if we pursue the study of biological rivalry between moulds and microbes, we may, perhaps, succeed in discovering still other facts which may be directly applicable to therapeutic science.' In this case, too, the search was not continued.

We see, therefore, that antibiosis was already a known phenomenon. But in 1928 the 'climate' of the scientific world was not the idea of penicillin, but he had the wrong mould, or the wrong bacteria, or both. If Fate had been kind to him, medical history might have been changed, and Lister might have lived to see what he had always been looking for - a non-poisonous antiseptic. From the time of Pasteur and Lister workers have been trying to kill one microbe with another. The idea was there but the performance had to wait until Fortune decreed that a mould spore should contaminate one of my cultures, and then for a few years more, until chemists busied themselves with the products of this same mould to give us pure penicillin. Lister would indeed have rejoiced to have had such a thing.' favourable to research along those lines. In fact, the reverse is true. All former experiments had demonstrated that every substance fatal to microbes also destroyed the tissues of the human body. This seemed almost self-evident. Why should a substance which was poisonous for certain living cells not be so, as well, for others, no less delicate?

cThe fact', said Fleming, 'that bacterial antagonisms were so common and well known hindered rather than helped the initiation of the study of antibiotics as we know it today.' Such facts no longer produced the least excitement, and gave birth to no hope of a new therapeutic development. More especially was the atmosphere hostile in Wright's department. The Chief was convinced that the only means of helping the natural defences of the body was still immunization. Fleming himself had shown by a brilliant series of experiments that all the antiseptics had proved abortive. He had discovered a natural defence, till then unknown — lysozyme. He had tried to increase its concentration in the blood, but without success. Outside the world of the greater parasites (trypanosomes, spirochaetes), Ehrlich's 'magic bullet' remained a dream. Wright could say again, as he had said in 1912, that 'the chemotherapy of human bacterial infections will never be possible ...'

Fleming, an observer without preconceived ideas, did, however, see a flicker of hope in his 'mould juice'. Might not the substance for which he had been looking all through his working life be found there? Though that distant flicker was, as yet, feeble, he decided to neglect nothing which might enable him to achieve success. He gave up all other work to concentrate on this research.

What he did has now to be described.


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