“The Mold That Changed the World” focuses on the physician who discovered penicillin. And it offers a message: Don’t take antibiotics unless you really need them.WASHINGTON — Robin Hiley’s eyes rolled when he recounted the night in 2016 that a friend, an infectious disease doctor, asked him what seemed like a crazy question: “Wouldn’t it be a great thing to have a musical about antibiotics?”Hiley, a composer and songwriter who is the artistic director of the Charades Theater Company in Edinburgh, was skeptical. Though the troupe calls itself “theatre with a social conscience,” antibiotics — or more precisely the threat of antimicrobial resistance, which can lead to death when common germs evade treatment — seemed a bridge too far.But the friend, Dr. Meghan Perry, was persistent, passionate about what she conceded was “this wacky idea.” And so it is that “The Mold That Changed the World,” a musical about Alexander Fleming, the Scottish physician and microbiologist who received a Nobel Prize in 1945 for discovering penicillin, is playing this week (through Sunday) in Washington.The show traces the life of Fleming, from his days as a young private in Britain’s Royal Army Medical Corps who later became a medical doctor, through two world wars and his famous discovery. It also offers a glimpse into a dark future — one predicted by Fleming himself — where antibiotics no longer work because deadly “superbugs” have learned to evade them.It also has a neat twist: a chorus of real-life health care professionals and scientists, who play soldiers, lab technicians, reporters — singing and dancing with the rest of the cast. They include people like Mario Sengco, a scientist at the Environmental Protection Agency who also sings in the Gay Men’s Chorus of Washington.Emily Bull, as Rose, comforts a wounded soldier played by Scott Armstrong in “The Mold That Changed the World.”Michael A. McCoy for The New York Times“How often can a musical deliver a lifesaving message to society?” he asked.The danger Fleming foresaw is, in fact, already here. Experts estimate that antimicrobial resistance leads to 1.2 million deaths around the world each year.And the problem — known by its initials, A.M.R. — is getting worse, because the drugs were overused during the coronavirus pandemic, said Dr. Rochelle Walensky, the director of the Centers for Disease Control and Prevention. (The show opens on Nov. 1 in Atlanta, home of the C.D.C.; Dr. Walensky will participate in a panel discussion before the performance.)At a discussion before Thursday night’s performance at the Atlas Performing Arts Center here in the nation’s capital, Dr. Rick Bright, former director of the federal Biomedical Advanced Research and Development Authority, made the story personal: After a cut he sustained while gardening led to an antibiotic-resistant infection, he spent a week in the hospital, and almost lost a thumb. It took seven antibiotics to cure him. Another panelist, the writer Diane Shader Smith, lost her 25-year-old daughter, who had cystic fibrosis, to a superbug infection.In Edinburgh, that is precisely what Dr. Perry was worried about when she pitched her idea to Hiley, who said he gravitates “toward historical stories that have a social impact.” He began reading about Fleming, he said, and “saw this potential of a story and started to begin to understand the global impact of A.M.R. And the seed was sown, so to speak.”The musical features a chorus of real-life health care professionals and scientists, who play soldiers, lab technicians, reporters — singing and dancing with the rest of the cast.Michael A. McCoy for The New York TimesThey received funding from the British Society for Antimicrobial Chemotherapy, which in turn led to backing from a powerful figure: Dame Sally Davies, who was then Britain’s chief medical officer. She was so concerned about antimicrobial resistance, she said, that it is now on Britain’s “risk register,” along with pandemics and bioterrorism, as a security threat.The show has had sold-out runs at the Edinburgh Fringe festival and has also played in London and Glasgow — with mold spelled “mould.” It opens with Fleming, played by Jeremy Rose, at the end of his life, encountering an otherworldly, barefoot Mother Earth figure named Rose, played by Emily Bull.Rose, the Mother Earth character, hovers over the story as a kind of narrator, bringing Fleming back and forward in time. Two ethereal-looking circus performers, dressed in flowing psychedelic colors, appear throughout the musical, spinning on an acrobat’s wheel. Hiley envisioned them as the “Gram twins,” representing two different types of bacteria: Gram-positive and Gram-negative. (Penicillin treats Gram-positive infections.)The audience sees the young Army private bidding farewell to the London Scottish Regiment, where he has served for 14 years. (“Private 6392, this mess hall honors you!” the cast sings.) Soon it is 1914, and Fleming is in Bologne, France, tending to soldiers — some from his old unit — facing death from exposure to poison and shrapnel wounds that turn into deadly infections.He cries at the uselessness of it all: “These men came to war prepared to die to protect their homeland, their families, their friends — not to be poisoned by gas, gangrene, harmless cuts; infected by horse manure on the fields on which they fought!”Fleming, later seen in his bacteriology lab at St. Mary’s Hospital in London, is a rumpled, earnest figure. He was apparently not the neatest of scientists, and the show riffs on other scientists who frown on his untidy habits. (“It’s clean and tidy we adore,” the chorus, dressed in lab coats, sings. “So sterilize those beakers! Disinfect that glass pipette!”) But that very untidiness led to his world-changing discovery.In 1928, while experimenting with common staphylococcal bacteria, Fleming spotted a ring of mold in a petri dish he had left by an open window while he was off on vacation. He was astonished to see that the mold had killed the germs. But that is not the end of the story.More than a decade passed before his discovery could actually be put to use. It took a couple of polished Oxford University scientists, Howard Florey and Ernst Chain, to purify the mold called penicillium notatum so that it could be tested on mice, and then people, and manufactured in mass quantities. They shared the Nobel with Fleming.A panel discussion at the Atlas Performing Arts Center included, from left: the composer and songwriter Robin Hiley; Sarah Despres of the U.S. Department of Health and Human Services; Bethany Brookshire, a science writer in Washington; Dr. Rick Bright; and the writer Diane Shader Smith.Michael A. McCoy for The New York TimesOne of the biggest challenges in modern medicine is that drug companies don’t want to invest in developing new antibiotics; it is not that lucrative, and if germs keep evolving to evade new drugs, the market potential is limited. In bringing the show to Washington, Dame Sally said, she hopes to persuade Congress to pass a bill, the PASTEUR Act, that would offer incentives for companies to innovate. (The name, a play on the famous scientist Louis Pasteur, stands for Pioneering Antimicrobial Subscriptions To End Up surging Resistance.)“We have a market failure,” Dame Sally said.Looking ahead, Dr. Walensky said, “addressing antimicrobial resistance is going to be the next chapter because it was the thing everybody was worried about before the pandemic.”As “The Mold That Changed The World” winds down, Fleming finds himself in the future, aghast at what humankind has wrought. With so many people taking antibiotics unnecessarily, and farmers using them to prevent and treat disease in livestock and increase productivity, modern medicine is no more equipped to handle bacterial infections than the young Fleming was on the battlefield.The message, Dr. Perry said, is clear: “Don’t take an antibiotic unless you really need it.” She harked back to when she and Hiley were brainstorming at the cafe in Edinburgh, and to the message she had written in block letters atop their storyboard: “Antibiotics are precious.” More