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When you have a sore throat, throbbing sinuses or a toddler with an ear infection, you’ll do just about anything to ease the pain. For most people, antibiotics — medicines that target bacterial infections — seem like a quick fix.

But taking a dose of amoxicillin, penicillin or any other mainstream antibiotic has both personal and societal risks. Using antibiotics can wipe out the healthy bacteria in your body, cause a range of side effects, including nausea, diarrhea and yeast infections, and contribute to skyrocketing rates of antibiotic resistance — the evolution of bacteria that evade treatment with drugs.

According to the U.S. Centers for Disease Control and Prevention, more than 2.8 million antimicrobial-resistant infections occur in the U.S. each year, killing more than 35,000 people. Climate change is thought to be exacerbating the problem, and scientists have reported that the COVID-19 pandemic worsened antibiotic overuse, with an increase in antibiotic prescriptions during the height of the pandemic despite the fact that COVID-19 is caused by a virus, which antibiotics don’t target.

With the winter illness season upon us, Stanford Medicine’s Alex Zimmet, MD, a clinical fellow in immunocompromised infectious disease and a member of the Stanford Antimicrobial Safety & Sustainability Program, ran down the list of things to know about antibiotics.

Can any antibiotic treat any bacterial infection?

No — which antibiotic is prescribed for which infection matters quite a lot. Just as different animals can differ in myriad ways, bacteria are a kingdom of organisms that differ across species. Most antibiotics target a unique structural aspect of bacterial cells, but some also target the ways that bacteria function or make proteins. Certain classes of antibiotics work for some bacteria but not others depending on whether the bacteria share those structures or functions being targeted. For example, the commonly prescribed antibiotic penicillin targets the bacterial cell wall, so those outside walls of the bacteria fall apart and the bacteria die. But some bacteria don’t have cell walls, so penicillin won’t have any effect. A major focus of learning to be an infectious disease doctor is learning those differences.

How do bacteria develop resistance to an antibiotic that once worked against them?

Bacteria that are exposed to the same antibiotic over and over are more likely to evolve resistance. Bacteria are constantly accumulating small mutations or picking up genes from other bacteria. If any of those changes help them evade antibiotics, they’ll survive, and those traits will be selected in the long run. Some bacteria gain resistance by altering the structure that an antibiotic targets so the drug no longer recognizes the bacteria. In other cases, bacteria can acquire a protein that destroys an antibiotic or quickly pumps it out. Once bacteria become resistant to multiple antibiotics, they can cause very hard-to-treat infections.  

Some doctors prescribe antibiotics “just to be on the safe side,” and some don’t for the same reason. What’s the thought process behind when to take them?

The reality of all decisions in medicine is that any treatment has some risks and some benefits, and we should give a treatment when the benefit outweighs the risk. That’s how doctors approach decisions about antibiotics. All antibiotics have side effects because they kill some of the healthy bacteria in your body along with any that are causing disease. Some antibiotics are very strong, and those side effects can end up being quite severe [such as diarrhea that leads to permanent colon damage].

Often, the decision about prescribing antibiotics comes down to how confident we are that someone has a bacterial infection rather than a viral or non-infectious illness. But figuring that out is a lot more complicated than the layperson would anticipate.

For example, a viral infection can lead to a bacterial one, and it can be difficult to know when the infection crosses that line where it suddenly requires antibiotics. That’s because a virus can cause damage that predisposes a person to other infections, including bacterial ones. You might have a viral sinus infection, which leads to a lot of destruction of the mucosa of the nose and a lot of new secretions, and then body fluids can’t empty out normally. That provides a good opportunity for bacteria to take hold when they might otherwise be expelled, resulting in a bacterial sinus infection. Similarly, if someone gets bad flu pneumonia (caused by the influenza virus), they’re more at risk of getting subsequent bacterial pneumonia.

Additionally complicating the diagnosis of an infection is that fact that a bacterial culture can’t always give us the answer. Say someone has the symptoms of a sinus infection, and we swab their nasal passages. Even if we find bacteria there, it doesn’t mean they have a bacterial sinus infection; many microorganisms live on and in our bodies all the time without causing disease. We often have to make a judgment call based on a person’s symptoms.

Is antibiotic overuse and antibiotic resistance something to worry about right now?

It’s a major problem. The World Health Organization has named antimicrobial resistance one of the top 10 threats to global health. A lot of that is attributed to antibiotic misuse and overuse, which happens not only in humans but also livestock and agriculture. Right now, bacteria are developing resistance to drugs faster than scientists are developing new antibiotics, so that is where the cause for alarm comes from. Antibiotic development isn’t like other domains of medicine where there are new drugs all the time; we have very few new antibiotics in the pipeline at all because it’s so hard to come up with effective new ways of targeting bacteria.

If you get an antibiotic-resistant bacterial infection, it can be much harder to treat effectively.

What can the average person do to combat the rise of antibiotic resistance?

Anyone should also feel comfortable engaging in dialogue with their doctor. If you think you have a bacterial infection that needs to be treated with an antibiotic and your doctor is saying no, you should feel encouraged to ask why and discuss the risks and benefits. If a doctor isn’t giving you antibiotics for your sinus infection, it’s not because they don’t care or don’t think you’re sick.

On the other hand, if you don’t want to take an antibiotic because you’re concerned about the consequences but your doctor is prescribing one, talk to your doctor about why they recommend it and how to minimize any side effects.

There’s a growing awareness of antibiotic resistance as a problem, and a lot more people are becoming educated about the impacts of antibiotics on things like their healthy microbiomes. Antibiotics used to be viewed as having only upsides, but now more people know about the downsides. I’d recommend that people just keep learning, being engaged citizens and paying attention to how things like national policies can impact antibiotic usage.

Photo: Fahroni