Technology & Medicine › Atomic & space age › Penicillin and antibiotics
Antibiotic resistance
warned 1945 (Fleming); MRSA 1961; now a global threat· Idea, religion or movement· Germs, drugs & genetics
Well documentedSolid records, physical evidence or scientific consensus.
Bacteria evolve to survive the antibiotics used against them, so once-curable infections can become hard or impossible to treat.
See it on the Technology & Medicine map →How it works
Every course of a drug kills the most vulnerable germs and leaves the toughest to multiply. Bacteria also swap resistance genes on small loops of DNA called plasmids. Fleming warned in his 1945 Nobel lecture that underdosing would breed resistance. Penicillin-resistant staph spread through hospitals by the 1950s, and MRSA, resistant to the newer drug methicillin, appeared in Britain in 1961. Overuse in medicine and in livestock speeds the process.
Why it mattered
Resistant infections directly caused an estimated 1.1–1.3 million deaths a year in 2019–21, and few new classes of antibiotics have reached patients since the 1980s.
Think of it like
Like spraying one pesticide season after season: the survivors breed, and soon the field is full of resistant pests.
How we know
Fleming's 1945 Nobel lecture, hospital lab surveillance since the 1940s, WHO global monitoring, and large studies in The Lancet (2022 and 2024) estimating deaths.
Still unknown or debated
How fast resistance will grow is uncertain; the widely quoted forecast of 10 million deaths a year by 2050 is disputed, and newer estimates are lower.
Connections (2)
▸Penicillin and antibiotics was undermined by Antibiotic resistanceWell documented
The connection
Bacteria that survive a drug multiply and pass on their defenses. Penicillin-resistant staph, which makes an enzyme that breaks penicillin apart, spread within a few years of mass use. Nearly every antibiotic since has met the same fate, usually within years to a decade of its launch.
When and how
Hospitals in Britain, the US and elsewhere from the mid-1940s; by the 1950s most hospital staph infections resisted penicillin.
How we know
In 1940 Edward Abraham and Ernst Chain found a bacterial enzyme that destroys penicillin, before the drug was in use; hospital surveillance has tracked resistance since.
Debates and open questions
Resistance genes long predate medicine: bacteria in 30,000-year-old permafrost carry them. How much human overuse, versus natural spread, drives today's crisis is still studied.
▸Deep learning (modern AI) has found new antibiotic candidates against Antibiotic resistanceMostly agreed
The connection
Deep-learning models trained on how known molecules affect bacteria can screen millions of untested compounds in days, work that would take labs years. In 2020 an MIT team found halicin this way, which killed many resistant bacteria in lab tests; later work found abaucin (2023) and a new class of compounds against MRSA.
When and how
MIT and the Broad Institute, Cambridge, Massachusetts (James Collins, Regina Barzilay), 2020–25; McMaster University, Canada (abaucin, 2023).
How sure are we?
Peer-reviewed papers in Cell and Nature report lab and mouse results; none of these compounds has yet completed human trials.
Debates and open questions
Whether AI-found compounds will survive costly human trials, and whether drug companies will pay to develop antibiotics that earn little, are open questions.