Updated on January 28, 2022.
Penicillin ushered in the antibiotic era when it was discovered in 1928. It and other antibiotics have saved the lives of countless people who would otherwise have died of infections. Now, though, many experts are worried that we may be entering a post-antibiotic era, where bacteria become immune to drugs and standard infection treatments no longer work.
Though it’s not a reality yet, in years to come, formerly treatable infections could once again turn deadly, and many forms of surgery might become extremely risky. The World Health Organization (WHO), in its 2014 Antimicrobial Resistance: Global Report on Surveillance, called the post-antibiotic era “a very real possibility for the 21st century.”
What is antibiotic resistance and how does it happen? What bacteria have stopped responding to drugs? And what’s being done to address the problem? We asked infectious disease specialist Seema Shah, MD, of Texas Orthopedic Hospital in Houston for her insights.
What causes resistance?
Antibiotic resistance happens when bacteria evolve so that antibiotic drugs can’t kill them anymore.
“Every type of bacteria has its own genome,” or set of genes and DNA, says Dr. Shah. “Mutations can occur in one bacterium that make it resistant to a type of antibiotic. Those start to multiply even if you’re taking antibiotics, because they’re not affected. And they can transfer that resistance to other bacteria.”
In other words, inappropriate overuse of antibiotics kills the bacteria that are not resistant but leaves alive the types that are resistant. The survivors can then, in a sense, teach other germs how to resist that drug.
In 2019, healthcare providers in the United States wrote 251 million outpatient oral antibiotic prescriptions, nearly enough for every American over age 18. The Centers for Disease Control and Prevention (CDC) estimates that at least 28 percent of antibiotic prescriptions are unnecessary.
But that’s a pretty small chunk compared to the amount of antibiotics used for livestock. In some countries, 80 percent of antibiotics that are used are given to animals, primarily to make them grow faster—a common effect of some of these drugs. In the process, bacteria in farm animals exposed to these antibiotics develop resistance over time. When humans eat the farm animals, they may pick up the resistant bacteria.
Which bacteria are fighting off antibiotics?
The CDC estimates that more than 2.8 million people per year get sick and 35,000 die in the US from resistant infections. Here are some antibiotic-resistant bacteria that are becoming more common—and more worrisome.
Staphylococcus aureus, commonly known as staph, lives on the skin and especially in the noses of many healthy people. Staph infections are usually minor, but they can be life-threatening if the bacteria enters your bloodstream, joints, bones, or vital organs. One type, methicillin-resistant Staphylococcus aureus or MRSA, is resistant to a number of common antibiotics, is particularly hard to get rid of, and can lead to sepsis or toxic shock syndrome. For now, MRSA can be treated with a few antibiotics, but it’s sometimes taking longer treatments or multiple antibiotics to knock out infections.
The group of bacteria called Enterobacteriaceae includes E. coli—a cause of food poisoning, as well as urinary tract and deadly bloodstream infections—and Klebsiella pneumoniae, which can lead to pneumonia, meningitis, and blood infections. Even the last-resort antibiotic carbapenem doesn’t work on some of these bacteria. Carbapenem-resistant Enterobacteriaceae top the WHO’s list of bacteria for which a new treatment is most desperately needed.
Certain strains of gonorrhea have become resistant to all but one class of antibiotics. “I don’t think it’s fair to say that resistant gonorrhea is common, but it’s becoming more and more of a problem in the last few years,” Shah says. The CDC has changed its treatment recommendations four times between 2010 and 2020 to account for increased resistance to a number of drugs.
Vancomycin-resistant enterococci (VRE) has been troubling healthcare providers for years, according to Shah. Enterococci infections often strike people who have already been hospitalized and are responsible for tens of thousands of hospital-acquired infections in the U.S. every year. In 2017, there were an estimated 54,500 VRE infections, of which about 5,400 were fatal.
What’s being done?
In June of 2017, the WHO’s Essential Medicines List got its biggest update in 40 years. In an effort to reduce overuse of last-resort antibiotics and lower the number of bacteria that become resistant to them, the list divides antibiotics into three classes.
- The “access” group consists of the most commonly used antibiotics, such as amoxicillin and azithromycin. They’re used to treat a wide variety of illnesses and should be available at all times.
- The “watch” group includes first- or second-line treatments for a smaller number of infections.
- The “reserve” group consists of last-resort treatments for when other antibiotics have failed to work.
The CDC has a similar effort with its hospital-based antibiotic stewardship programs.
As for antibiotics on farms, the European Union outlawed the use of antibiotics to promote growth in animals in 2006. The U.S. Food and Drug Administration (FDA) regulates antibiotic use. The Veterinary Feed Directive rule, which kicked in on January 1, 2017, requires a veterinarian to supervise medically important antibiotics when they are used on any food animal species, such as livestock or poultry—whether or not that animal is raised as food. It is also illegal in the U.S. now to use medically important antibiotics on animals purely to get them to grow.
Overuse of antibiotics on farm animals is widespread in low- and middle-income countries, however, and recent research has detected “hotspots” of antibiotic resistance in India, China, and many other countries.
On October 8, 2020, the U.S. government released a five-year plan to combat antibiotic-resistant bacteria. It aims to better detect resistant bacteria, speed up research, and improve collaboration among the many groups involved with this problem, including healthcare and veterinary professionals, farmers, researchers, and industry.
But fighting antibiotic resistance is slow work, and meanwhile, the pace of developing new antibiotic drugs has been slow.
“There’s not a lot of incentive for drug companies to make these new antibiotics,” says Shah. Drug companies haven’t been heavily investing in the research since there’s little chance to make money.
In recent years, some new antibiotics have arrived. But this type of research is unlikely to keep pace with the global scale of bacterial resistance, and efforts to get at the root of the problem are continuing.
