What to Know About Antibiotic Resistance

For thousands of years, people around the world have used plants and other natural medicines to treat bacterial infections. But it wasn't until the 1940s, following the discovery and mass production of penicillin, that antibiotics became the gold-standard treatment.

Since then, antibiotic medications have been so widely used that many bacteria have become immune to them, causing infections that are increasingly difficult to treat. By the year 2050, untreatable infections are expected to cause over 10 million deaths per year—the same number of deaths caused by cancer in 2020.

"Antibiotic resistance is a huge public health crisis," says Daniel Green, MD, a microbiologist at Columbia and co-director of the Clinical Microbiology Laboratory. "Every time you take an antibiotic, you're giving the bacteria in your body an opportunity to become resistant to medications."

Dr. Green draws from his expertise in microbiology research and diagnostic testing to explain how antibiotic resistance develops, who's most at risk, and simple steps you can take to help slow the spread.

How do bacteria become resistant to antibiotics?

Antibiotics are designed to either kill bacteria or stop them from growing. But bacteria are incredibly adaptable organisms, and they evolve quickly. By random chance, some bacteria naturally develop genetic mutations that protect them against these kinds of threats.

If you have an infection, antibiotics will wipe out most of the bacteria making you sick. But a few resistant bacteria can survive and multiply, spread, and even share the genes that helped them resist the drug with other bacteria. This causes infections that are much harder to treat because the antibiotics that are normally used won't affect these bacteria.

So, the antibiotic itself doesn't make the bacteria resistant—the exposure to it simply reveals which bacteria are already resistant and gives them a survival advantage.

Some bacteria are resistant to only one kind of antibiotic, while others can become resistant to many (known as "multidrug resistance").

How common is it for bacteria to become resistant to antibiotics?

It depends on the type of bacteria. Strep throat, for example, is caused by a bacterium called Streptococcus pyogenes and is treated with amoxicillin. Despite nearly a century of widespread use, S. pyogenes has remained susceptible to amoxicillin. how long is strep contagious after amoxicillin is a common question patients have, and understanding resistance patterns helps answer it.

However, there are other bacteria that more commonly acquire resistance, such as Klebsiella pneumoniae, which can cause pneumonia, urinary tract infections (UTIs), and sepsis. In New York City, up to 10% of K. pneumoniae bacteria are "superbugs" that are resistant to the most common antibiotics.

Hospitals are one of the biggest sources of antibiotic-resistant bacteria. Hospitalized patients often have weak immune systems, so they're given antibiotics to treat infections they acquire while in the hospital or to prevent them from getting infections in the first place. The bacteria in those patients develop resistance and can quickly spread within the hospital to other sick patients. Some of these bacteria can become resistant to multiple antibiotics, making them especially dangerous.

Some of the most common illness-causing bacteria in hospitals include:

• Clostridioides difficile: can lead to severe and sometimes fatal diarrhea known as C. diff colitis
• Enterococcus species: can cause bloodstream infections, UTIs, and surgical wound infections
• Staphylococcus aureus: can cause several types of antibiotic-resistant staph infections, including MRSA; nearly 40% of all staph infections in hospitals are caused by MRSA.

Who's most at risk for catching an antibiotic-resistant infection?

Anyone can get an antibiotic-resistant infection, but people who have underlying medical conditions or weakened immune systems are especially vulnerable. Being hospitalized repeatedly or for a long time is also a significant risk factor.

How is a bacterial infection that isn't responding to antibiotics treated?

The first step is to identify the bacteria causing the infection, which is done by taking samples from the patient and growing the bacteria in the lab. Then, we expose these bacteria to commonly used antibiotics to see what kills them and what doesn't. These data let providers choose the right medication for that specific patient.

When bacteria are immune to many antibiotics, the infections they cause are much harder to treat. We have newer antibiotics that can target them, but we use those drugs very sparingly because we don't want to promote resistance to them, as well.

Can't we just develop more or stronger antibiotics that kill resistant bacteria?

Unfortunately, it's very time-consuming and expensive to develop new antibiotics. One alternative is using viruses to kill bacteria, known as phage therapy. This approach has been used for decades in some European countries but isn't FDA-approved for use in the U.S. Phage therapy has its own limitations, but we're starting to revisit it as a possible path forward.

What can I do to avoid creating and spreading antibiotic-resistant bacteria?

The more antibiotics are used, the more bacteria become resistant. These four steps can protect you and help slow this global crisis:

• Ask your doctor whether you really need antibiotics when you're sick. Many doctors prescribe antibiotics for respiratory viruses like the common cold and flu, but antibiotics don't work against viruses. This leads to unnecessary exposure.
• Take the full course of antibiotics when you're prescribed them, even if you start feeling better before you finish them. Not taking all of the medication means only some of the bacteria will die, which can make you sick again and can allow the bacteria to more easily develop resistance to that antibiotic.
• Don't share antibiotics. When you and a loved one get sick at the same time, be sure that each sick person seeks medical care to get their own diagnosis and prescription. You may be sick with different infections that cause similar symptoms, and taking someone else's antibiotics means neither of you will complete the full course.
• Practice good hygiene by washing your hands frequently, not sharing personal care items like razors or towels, and regularly disinfecting your home. does heating kill bacteria is another important question to consider as part of everyday hygiene habits.

Antibiotic resistance is not something new—it's been happening since shortly after the first antibiotics were developed. The best thing we can do is be judicious about when and how we use them. Antibiotics are a precious resource that have transformed medicine, and we all have a shared responsibility to use them wisely.

Daniel Green, MD, is an associate professor of pathology and cell biology at the Columbia University Vagelos College of Physicians and Surgeons and the co-director of Columbia's Clinical Microbiology Service.