The Great Golden Age of Antibiotics

Over half of the therapeutic antibiotics used today were discovered in a brief 20-year period. A fortuitous discovery in the 1940s led to a global rush for miracle medicines in the soil. That wondrous method ended in the late 1960s. And unfortunately we have yet to find another. In today's video, let us look back at the golden age of antibiotics when people spanned the globe for the next big drug. ## Beginnings In 1928, Alexander Fleming famously noticed that a spot of mold was killing bacteria in one of his Petri dishes. It is important to note however, that it has long been known that chemicals in molds can kill or inhibit bacteria. Like really long known. The ancient Egyptians applied moldy bread to help burns, for instance. And Joseph Lister in the 1800s knew that the mold Penicillium glaucum can somehow inhibit bacterial growth. The physicist John Tyndall wrote a paper about the effects of mold in tubes of bacteria. Drugs have even been found and sold with strong anti-bacterial properties. In the early 1900s, the Nobel winning physician and scientist Paul Ehrlich discovered Salvarsan. Derived from the poison arsenic, Salvarsan was the first drug found to be effective against syphilis - which then afflicted a sixth of all Parisians and a tenth of all Londoners. It also works against a few other diseases. But the larger issue was the drug’s toxicity - severe enough to potentially kill the patient too. This leads to a key point about drugs. It is not enough to be effective. It also can't be toxic. It must be able to reach a good concentration inside the body after intake (bio-availability). And it must be stable enough to remain as such in the body until the job is done. ## Fleming's Discovery So anyway, after Fleming noticed the bit of mold in his petri dish, he sought to isolate the material but failed. So he published his findings the following year. And nobody really cared. People acknowledged that mold can kill or inhibit bacterial growth, but considered therapeutic use at commercial scale impractical. This changed in the late 1930s when a team of scientists at Oxford University - Howard Florey, Norman Heatly and Ernst Chain - managed to identify and extract the antibiotic. They then ran a trial on mice that was a phenomenal success. In 1940, they published their results. The drug later hit the market in 1943 with great success, saving many lives and inspiring a search for similar drugs. ## Waksman and Streptomycin Our story now turns to an Ukrainian-born American named Selman Waksman. Waksman was then a professor at Rutgers University and one of the best soil microbiologists of his day. One day in 1939, two pieces of news reaches him. The first was that one of his students, Rene Dubos, had isolated a new antibiotic at the Rockefeller Institute. This antibiotic is now known as tyrothricin, used for treating minor skin wounds. Interestingly, Dubos found the drug by systematically feeding colonies of pathological bacteria to mixed samples of soils. The idea being to find a chemical in those soils that can kill that bacteria. At the same time, Waksman hears that the British had successfully isolated and purified penicillin - making it useful therapeutically. Waksman put the two together and has an idea. In an oral history, student Woodruff Boyd recalls Waksman saying to him: > "I know that my favorite organism, the actinomyces, will do better [than Penicillin]... Drop everything you're doing and start isolating some streptomyces and see if you can find an antibiotic that's better than penicillin. " The actinomycetes are a family of complex soil bacteria. Streptomyces refers to a genus within that family, encompassing several hundred known species. So Waksman and his team collected thousands of soil bacteria and cultured them on agar plates seeded with pathogenic bacteria. Team members would then visually scan the plates for spots where the growth of that pathogenic bacteria seem to have been inhibited - a sign of antibiotic activity. A simple mechanism performed at great scale. In 1940, this method yielded a new antibiotic candidate called Actinomycin. Despite it being effective against a broad range of bacteria including tuberculosis, the drug turned out to be too toxic for therapeutic use. Small note of interest. Much later, Actinomycin was found to have anti-cancer abilities and a variant of it is used for chemotherapy today. Eff cancer.

Despite this setback, the discovery encouraged Waksman and his corporate partner Merck enough to expand their efforts. The screening continued - eventually leading to the discovery of a new drug called Streptomycin in 1943. Streptomycin is widely acknowledged as the second great antibiotic after penicillin itself. And the first shown to be effective against the dreaded disease tuberculosis. Soon afterwards, a dispute emerged on who deserved credit. One of Waksman's students - Albert Schatz - had been the one who ran the actual experiment to uncover the Streptomycin drug. He later sued for co-authorship credit and a financial stake in the drug’s royalties. Most of the royalties went to a foundation. But Waksman took a 20% share and earned from it what is now about $4. 5 million a year. In the settlement, that 20% split was amended. Waksman would get 10% of the royalties. Schatz received 3% share plus co-discovery credit on the drug's patent. Elizabeth Bugie Gregory, who independently verified the results and so was listed as a co-author on the first streptomycin paper, also received a 0. 2% share. The remaining was evenly dispersed amongst the lab's members. ## A Systematic Search In 1952, Waksman won a Nobel Prize in Medicine. Debate and ethical discussions remain over whether Schatz should have shared the Nobel too. But Waksman’s Nobel Prize citation hints at what I find to have been most significant about Waksman's work, historically speaking. The citation noted that while penicillin’s discovery was by pure chance. Streptomycin’s discovery on the other hand came about via a sophisticated method that was targeted and scalable. I quote: > In contrast to the discovery of penicillin by Professor Fleming which was largely due to a matter of chance, the isolation of streptomycin has been the result of a long-term, systematic and assiduous research by a large group of workers. So the big deal wasn't necessarily the discovery of the drug itself, though that was certainly important. Rather, it was Waksman producing a systematic search methodology. From then on, antibiotics discovery would be a team effort, no longer dominated by the solitary figure in the lab. It already was kind of the case with streptomycin. The antibiotic was found in two strains of bacteria. The strain more effective at producing the drug came out of a chicken's throat. A student named Doris Jones Ralston swabbed and cultivated the sample before handing it to Schatz. Does she deserve credit too? This was Waksman's point. Schatz spent a total of three months in Waksman's lab performing the same protocols as everyone else. If anything, Bugie probably deserves more of a share than what she got. Was he right? I shall leave that to your own determination. Regardless of whatever, my readings of the accounts of Waksman's actions find him to have acted like an ungenerous a-hole. ## The Special Soils As mentioned, Streptomycin is produced by a species within the Streptomyces genus of the actinomycetes family. The 700 species in this genus have provided two-thirds of the naturally occurring antibiotics used today. What about these soils and bacteria that make them so conducive for producing new drugs? There has been much debate over the years about this. One early idea was the "Great War" theory. Soils host hundreds of millions of bacteria, protozoa, algae, and fungi - creating an intense competition for scarce resources like space or nutrients. So early on, people surmised that soil bacteria evolved these antibiotics to defeat rivals in vicious combat for those resources. That view has somewhat evolved over the years. Studies have shown that antibiotics serve multiple purposes. For instance, antibiotics at low doses seem to be used as signals. Signs that things are changing in the neighborhood and that nearby bacteria have to start preparing. Or they can be a signal to rivals that this particular area is occupied. But it is true that in high stakes situations - like during competition for a spot in a local nutritious niche in the soil - the bacteria can ramp up the antibiotic dose to defend its position. ## The Great Antibiotic Race Anyway. Waksman's discovery set off the Great Antibiotic Race. Over the next twenty years, pharmaceutical companies scoured the globe for soils to produce the next great antibiotic. The Waksman team at Rutgers screened hundreds of thousands of microbes drawn from these soils. Some samples came from far away. The thinking was that the rarer and more exotic the locale

the more likely to find something new. Employees taking trips or vacations abroad were encouraged to bring sampling bags with them so they can bring soils back. This certainly worked at times. The antibiotic Erythromycin came from a soil sample in the Philippines. The first broad-spectrum oral antibiotic chloramphenicol came from a soil sample collected in 1947 near the city of Caracas in Venezuela. The Italian company Lepetit discovered the antibiotic rifamycin from a sample collected in the French city of Saint-Raphaël by a vacationing employee. Rifamycin derivatives are still used to treat traveler's diarrhea and tuberculosis. And most famously, the antibiotic Vancomycin was discovered in 1952 in a soil sample from the forests of remote Tengeng, Borneo collected by a Christian missionary. But plenty came from the companies' own backyard. A member of the drug company Pfizer discovered a drug called Oxytetracycline in a soil sample collected just outside their lab in Terra Haute, Indiana. It would be marketed as Terramycin - named after where the original sample came from. The drug's success transformed Pfizer from a mildly successful producer of citric commodities for the food industry into a pharmaceutical giant. After collecting the samples, a streak of the unknown actinomycete would be put in a standard petri dish. The pharmaceutical companies employed experienced soil microbiologists to identify such actinomycete by eye. And then various pathological bacteria and fungi would be put at right angles to the actinomycete streak. The bacteria to be tested usually was whatever was the main concern of the day. After a few days, a technician would evaluate the petri dish for signs of antimicrobial activity. Meaning whether the growth of the pathological bacteria had been impeded in some way or form. And remember, since this was the late 1940s and 1950s, there were no automated systems or Tesla Optimus robots to handle this. It had to be all done by hand. The hit rate for these screening programs was extremely low. Eli Lilly studied over a million isolates over 30 years. Out of that million, Vancomycin was one of just three antibiotics eventually brought to the market. And Pfizer screened over a hundred thousand candidates, but Terramycin would be the only antibiotic from that program to make it to market. Most turned out to be duplicates or were too toxic. ## The Golden Era Ends In the 15 years after 1943, Streptomyces produced basically one new useful drug each year. The number of new drug discoveries likely peaked in the late 1950s. Afterwards, researchers started finding the same drugs over and over again - despite persistent efforts. Between 1947 and 1956, there were 606 papers published proclaiming the discovery of a new antibiotic. 163 turned out to be duplicates. Between 1957 and 1967, the number of duplicates surged to 253. A quarter of all previously discovered drugs were then "rediscovered" at least once. Some like streptothricin - a toxin produced by 10% of all soil microbes - were rediscovered as many as 19 times. By the late 1960s, it became clear that the soil mass-screening model had run its course. This was a major problem because antibiotic-resistant bacteria were already emerging in the 1950s. Particularly in hospitals, where that emergence was quite rapid - driven by microbes like Staphylococcus aureus. One hospital in 1951 had just 4. 8% of its cases resistant to tetracycline and aureomycin. Two years later, that had risen to 78%. One troubling case in September 1952 saw no strains of bacteria resistant to the aforementioned erythromycin. A month later, those resistant strains began to emerge. And by January, they were all resistant. In response, doctors turned to multi-drug therapies starting in 1953 - hoping that combinations can hit bacteria from multiple sides and limit their evolution towards resistance. But such a thing only worked for so long. ## Hamao Umezawa One of the scientists facing this growing resistance was Hamao Umezawa (梅澤濱夫), born the fourth in a line of doctors. Near the end of World War II, Umezawa led a team of biologists to help Japan be the

third country in the world to domestically produce penicillin - a critical resource in the days following the war. He then pivoted to discovering new drugs. Umezawa at first followed Waksman's methods of mass screening soil-dwelling actinomycete bacteria. But as resistance to drugs like streptomycin became more common, he shifted his screening targets to addressing this resistance. He was rewarded with the antibiotic kanamycin, which initially defeated streptomycin-resistant tuberculosis. Kanamycin became Japan's first exportable antibiotic, and the drug's royalties help fund work at the Institute of Microbiological Chemistry in the coming years. When Waksman's methods started to lose their effectiveness in the late 1960s and early 1970s, Umezawa retooled. Studying Kanamycin resistance, he notices bacteria producing two enzymes that disrupt the drug's effectiveness. So he synthesizes a new drug that works like Kanamycin but evades those enzymes by removing a specific hydroxyl group - dibekacin. When the bugs became resistant to that one too, he creates arbekacin - which attaches a special side chain to dibekacin to make it effective again. Throughout his illustrious career, Umezawa produced nearly seventy antibiotics targeting bacteria. At the same time, he realizes that antibiotics can inhibit the growth of cancer cells too. His work discovers nearly 40 anticancer antibiotics, including Bleomycin - used for Hodgkin’s Lymphoma and testicular cancer. In the latter, Bleomycin makes one leg of a three-way therapy called BEP that turned testicular cancer from a near-certain death sentence to a highly curable situation. Literal game changer. Umezawa passed away in 1986 after a life well lived. In terms of sheer number of drugs discovered, he stands above perhaps even the great Selman Waksman. ## Semi-synthesis When the soils finally ran dry, drug chemists like Umezawa turned to the "semi-synthetic" method. This worked by modifying or improving known molecules called scaffolds to create new drugs. So you take a natural drug molecule, strip it down to its effective core, and then add new side chains to give it a twist. Candidates are then screened for factors like improved bio-availability, effectiveness against resistance, or safety. I already discussed Umezawa producing variants to evade Kanamycin-resistance. Another example of this is the adding of hydrogen to streptomycin to create dihydrostreptomycin, a more chemically stable variant. Semi-synthesis was very successful - crucial in maintaining antibiotic effectiveness even as resistance continues to expand. It has turned the original penicillin into its own whole class of drugs called beta-lactams. And today, beta-lactams make up 60% of all the drugs used for treatment and 65% of the approximately $15 billion antibiotic market. But these new methods cannot help accelerate the discovery of new classes of antibiotics. The number of which coming to the medical market has slowed to a crawl. Several were actually discovered all the way back in the golden age. ## Conclusion The soils were so effective in producing new antibiotics because it combined high microbe population density with fierce competition for food and resources. And collecting soil samples were simple. Is there another treasure trove like it out there? Researchers have suggested a variety of different environments: Within sponges, marine invertebrates, and insects. Lichens, gut bacteria have also been suggested. But perhaps first the economic incentives for finding new antibiotics must change. In the 1980s, there were twenty pharmaceutical companies working on discovering new antibiotics. That has since dwindled to only a handful. The economic incentive for a new antibiotic has somewhat diminished because it is a cheap cure and getting a drug to market takes years and many millions of dollars. But the demand from patients persists. Two million Americans are infected by antibiotic-resistant diseases each year. An estimated 20,000 will lose their lives to it. The need for new drugs is urgent.