How Come Bacteria Never Seem to Evolve Resistance to Bleach?

We’ve all heard that bacteria are becoming resistant to all our antibiotics and it’s a huge problem. That said, at my job we still sanitize surfaces with the same old chlorine bleach solution folks have been using for at least 50 years. How come bacteria never seem to evolve resistance to that? —The Bleach Boys

Fifty years is an understatement, Boys. Pioneers like Dr. John Snow were using chlorine bleach to disinfect contaminated water as early as the 1850s. (Snow also invented epidemiology, discovered the cause of cholera, and hipped British surgeons to a radical new concept called “anesthesia”—not bad for a guy whose name is synonymous with knowing nothing.)

To explain the difference between antibiotics and bleach, let me tell you about my car. Old Hondas are notoriously easy to steal, so I’ve modified mine with a relay that interrupts a circuit the car needs to start. It’s a minor change, but it ensures that no one but me can start the car.

Antibiotics are like that relay: They’re designed to attack one critical system very efficiently while leaving everything else intact. It’s a nice, targeted, non-invasive way of attacking the problem—but of course, if the bacteria (or the car thieves) figure out a way around your little stratagem, it’s back to square one.

Bleach works differently. If antibiotics are like keeping your car from getting stolen by using a secret kill switch, bleach is like keeping your car from getting stolen by blowing it up with a small nuclear bomb. Sure, your entire neighborhood may be a smoking pool of molten glass, but try getting that Honda now, you dirty tweakers!

In other words, bleach destroys cells—including yours—indiscriminately. This is great when you’re trying to sterilize an operating table, but not so hot when you’re trying to clear up a 6-year-old’s eye infection. (It’s also why curing COVID by injecting Clorox directly into your veins doesn’t work.)

Still, it’s precisely this “Kill ‘em all; let Dr. Fauci sort ‘em out” attitude that has made bleach so enduringly effective. It doesn’t need to focus on any particular system or process; it’s strong enough to chemically dismantle any protein or lipid structures the cell might be made of, essentially doing to bacteria what Jesse Pinkman did to that dead guy in the bathtub in Breaking Bad. Good luck evolving resistance to that.

Questions? Send them to dr.know@wweek.com.