Fight viruses in your home without making bacteria stronger

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Understandably, everyone’s got SARS-CoV-2—the coronavirus behind the COVID-19 pandemic—on their minds. But even amidst a global emergency, we should take care not to forget the existence of the countless other microbes that surround us.

Not all bugs are bad (in fact, trillions exist on or inside us that we can’t survive without). But many of the microbes that do cause disease have developed the ability to thwart the drugs we use to treat them. In the United States alone, about 2.8 million antibiotic-resistant infections arise each year, resulting in more than 35,000 deaths—and the threat could worsen if we’re not careful about the cleaning products we use to battle the current viral outbreak.

“Antibiotic resistance is one of the biggest global health challenges out there right now,” says Erica Hartmann, an environmental microbiologist at Northwestern University. “It’s important that we take this opportunity to critically evaluate how we’re cleaning.”

How antibiotic resistance works

To smack down SARS-CoV-2, you need little more than soap and water, or, in a pinch, an alcohol- or bleach-based disinfectant. All of these substances will break down many types of microbes through brute force, physically dismantling bits of their anatomy.

Some common household cleaners and disinfectants, however, include extra ingredients: antibiotics and antimicrobials. Companies toss these additives into the mix to (theoretically) up a product’s killing capabilities, but they’re only effective against certain bacteria and fungi. That means these chemicals aren’t just useless against the new coronavirus (and all other viruses, for that matter)—they could also cause drug resistance in other types of pathogens that could come back to plague us in the future.

Deployed in the right context (by a doctor treating a patient’s bacterial infection, for example), antimicrobials do work, often by disrupting a specific, vital piece of a microbe’s cellular machinery. And in the century since their discovery, these compounds have prompted an unprecedented plunge in infectious diseases worldwide.

But bacteria and fungi are highly adaptive organisms with diverse populations. A wave of antibiotics might wipe out most of them, but the rare microbes with genetic mutations that render them impervious to a drug will survive and multiply, seeding a new community of hardier, tougher-to-treat bugs. The more people use antibiotics—and the more they use them improperly —the more chances bacteria have to persevere.

Whenever unnecessary antimicrobials find their way into cleaning products and disinfectants, these microbes get another opportunity to adapt, Hartmann says. Sprayed liberally onto household surfaces, these potent liquids will linger and persist, all while losing potency—a perfect storm for tenacious bacteria to grab a foothold and multiply.

From there, the risks only grow. “The biggest concern is that those resistant microbes [themselves] are infectious,” Hartmann says. If drug-tolerant pathogens find their way into a human body, they’ll kick off an infection that’s more challenging to treat. (Weakened by virus, patients with bad cases of COVID-19 are often more vulnerable to bacterial infections, which can make the disease worse.)

Even benign bacteria with drug resistance can cause issues down the road. If these microbes mingle with other strains or species that do cause disease, they may end up exchanging genetic material that passes their tolerance on to others, Hartmann says.

Cleaning products spiked with antimicrobials aren’t the only culprits driving antibiotic resistance. These compounds are found in a dizzying array of commonplace items—and by and large, they’re not actually doing much to boost the sanitizing properties of the objects they’re in. Soap—a substance that’s already naturally good at fighting microbes—is an especially good example: It simply doesn’t need extra chemicals to do its job.

“There may be a conception out there that if chemicals are really strong, that must mean they’re better—that’s not necessarily the case,” says Ariangela Kozik, a microbiologist at the University of Michigan. “Throwing chemicals at everything is not going to fix the problem.”

Hartmann recommends paying close attention to any labels that say “antibacterial” or “antimicrobial.” Compounds can also lurk less prominently in ingredient lists. Some websites, like this one from the Green Science Policy Institute, provide some guidance on how to spot them.

Stick with the basics

There are a lot of products branded with marketing that plays into people’s fears about the pandemic, Kozik says. Instead of literally buying into the hype, we should trust the familiar, time-tested compounds we know will work to keep us safe. In this case, that means sticking to basics like soap, alcohol, and in some cases, bleach.

To keep pathogens like the coronavirus at bay, turn first to soapy suds and water—a combo that both damages microbes and removes them from surfaces. You can also spray or wipe objects with a disinfectant that’s at least 70 percent alcohol. Diluted bleach solutions work too, though neither Hartmann nor Kozik is as keen on these because they’re so harsh on human cells. (If you use them, keep the room ventilated—and please don’t mix them with other cleaning products.)

While microbes can develop resistance to drugs that target specific parts of their life cycle or anatomy, the same isn’t true of soap, alcohol, and bleach, which are general physical and chemical methods of disrupting bacteria and viruses, Hartmann says. Escaping an antibiotic might only require a microbe to modify the shape of a protein so a drug no longer affects it. Avoiding soap-based destruction, on the other hand, would require something far more drastic—on the order of growing an iron cage around its cell.

As many of us hunker down in our homes with hygiene on the brain, Hartmann recommends focusing cleaning efforts on commonly touched surfaces like doorknobs, faucets, and toilet flush handles to stem the spread of disease. That’s doubly true if anyone in your household has been exposed to SARS-CoV-2 and may be at risk of shedding virus onto surfaces. But if not, there’s “no reason to go crazy” on the cleaning, Hartmann says.

It’s also possible to overdo it: In recent years, scientists have come to realize that grime, grit, and germs are actually pretty important for training our immune system during childhood. The beneficial bacteria that help our bodies function on a daily basis could suffer from overexposure to cleaning compounds.

COVID-19 aside, these are good principles to follow even when the world isn’t in the middle of a pandemic, Hartmann says. After all, our microscopic roommates aren’t moving out anytime soon.