Antibiotic resistance happens when bacteria develop a defense against one, or multiple antibiotic drugs.- Antibiotic resistance is dangerous because it can make infections, like UTIs, harder to treat.
- The overuse of antibiotic drugs in agriculture and medicine has is the main cause of antibiotic-resistant bacteria.
- This article was medically reviewed by Tania Elliott, MD, who specializes in infectious diseases related to allergies and immunology for internal medicine at NYU Langone Health.
- Visit Insider's Health Reference library for more advice.
In 1942, a patient named Anne Miller made medical history. She was on the brink of death from a bacterial infection in her blood, called septicemia, when doctors treated her with a new drug, penicillin.
Penicillin is the world's first mass-produced antibiotic drug, and Miller's life was the first of many it has saved. It's not an understatement to say that mass-produced antibiotics are one of the greatest life-saving developments in human history.
However, Alexander Fleming, the scientist who discovered penicillin in a moldy Petri dish in 1928, quickly recognized that the drug may spawn a catastrophic problem — antibiotic resistance.
What is antibiotic resistance?
Antibiotic resistance occurs when bacteria evolve defense mechanisms against one, or multiple, types of antibiotics. Bacteria are simple organisms that generally reproduce every few hours, and therefore can quickly adapt and mutate.
So, when an antibiotic doesn't eliminate 100% of bacteria from an infection, the remaining survivors may evolve protective genes against the drug. They can then pass these genes on during reproduction. But they can also pass the genes amongst each other through a process called horizontal gene transfer.
Bacteria have had hundreds of millions of years to evolve ways to deal with naturally occurring antibiotics. "We discovered antibiotics, but we did not invent antibiotics," said Joanna Slusky, a molecular biologist at the University of Kansas. In her research, she looks for ways to disable drug resistance in cells so existing antibiotics can still work.
As soon as most antibiotics were introduced, scientists discovered bacteria resistant to those drugs almost immediately. For example, the antibiotic methicillin and methicillin-resistant Staphylococcus aureus (MRSA). Methicillin was introduced in 1960, and resistance was detected in 1962. This is not unique: There are bacterial pathogens that are resistant to nearly every single antibiotic in existence.
Well-known pathogens like Mycobacterium tuberculosis — the bacteria that cause the disease tuberculosis — are now resistant to many antibiotics commonly used to treat it. As a result, this has led to a more deadly, albeit rare, form of the disease called extensively drug-resistant TB.
Between 1993 and 2011, there were 63 cases of extensively drug-resistant TB in the US. But there is another specific drug-resistant bacteria responsible for almost 13,000 deaths a year: Clostridium difficile.
This bacteria, commonly known as C. diff, causes life-threatening intestinal issues and is one of five pathogens classified as an "urgent threat" by the Centers for Disease Control and Prevention. In addition, this pathogen alone was responsible for an estimated $1 billion in healthcare costs in 2017.
Why is antibiotic resistance a problem?
Even though deaths related to antibiotic resistance have decreased over the past decade, according to the CDC, it remains one of the most significant public
Unlike the novel coronavirus pandemic, which struck suddenly and unexpectedly, antibiotic resistance has been a growing problem for decades. In a 2019 report on antibiotic resistance, CDC director Robert Redfield plainly states: "Stop referring to a coming post-antibiotic era — it's already here."
Antibiotic resistance is not only deadly, it also makes common infections, like UTIs, harder to treat. "E. coli causes 80% to 90% of urinary tract infections, so we are seeing more antibiotic-resistant E. coli causing simple UTIs," says Elizabeth Hirsch.
Hirsch is an experimental and clinical pharmacologist at the University of Minnesota who runs a lab that studies mult-drug resistant Gram negative pathogens, like E. coli. Gram negative bacteria have an outer cell membrane that makes it difficult for antibiotics to penetrate, says Hirsch.
Now that E. coli is no longer susceptible to many commonly-prescribed antibiotics, healthcare providers may need to take extra steps toward prescribing the right antibiotic. In the past, a healthcare provider would prescribe an antibiotic for UTI without culturing the bacteria in the urine, she said. Now, they may want to find out the specific bacteria causing the infection so they can be sure the prescribed drug will be effective.
It's not just simple infections — surgeries and other invasive procedures that increase a person's risk of infection could reach a tipping point. According to the CDC, a growing number of healthcare-associated infections are caused by antibiotic resistant pathogens.
"Hospitals will be much scarier places. You might get infections that can't be treated," Slusky said. Deaths from antibiotic-resistant infections in hospitals have decreased according to the CDC, but healthcare settings still need to take rigorous measures to make sure the problem does not overwhelm hospitals in the future.
What causes antibiotic resistance?
The overuse of antibiotics is what causes antibiotic resistance. From hospitals to agricultural fields, entire industries need to reconsider how they use antibiotics to curb the proliferation and creation of resistant bacteria.
In 2014, 17,000 tons of antibiotics were used in US agriculture, alone, which was 80% of total antibiotic use in the country. While these antibiotics are given to livestock, experts say this impacts humans because drug-resistant bacteria spillover into waterways and soil, and also infect those who work on farms. Slusky put it plainly: "More antibiotics that are out there means there are more opportunities for bacteria to develop resistance."
People also need to stop using antibiotics to treat viruses and other conditions — antibiotics only help on bacterial infections. The CDC estimates that in up to 50% of cases where antibiotics are prescribed unnecessarily.
Just in the ICU alone, studies show 30% to 60% of antibiotics prescribed are "unnecessary, inappropriate, or suboptimal." In some states, the number of antibiotic prescriptions per year averages out to more than one prescription per person.
The future
Countries in Europe are taking action against antibiotic resistance through the European Antimicrobial Resistance Surveillance Network. The program has been tracking antibiotic use for the past 20 years in countries throughout Europe, and allows epidemiologists to examine trends in antibiotic use to better understand the scope of the problem. The US has no such surveillance system for antibiotics.
As for developing new antibiotics to take the place of old ones that are no longer effective — that prospect is grim. There are not many new antibiotics on the horizon. Most classes of antibiotics were introduced before 1970, and there is not much of a financial incentive for pharmaceutical companies to invest in new drugs that are meant to be used sparingly to reduce the evolution of resistance.
There are 41 antibiotic drugs in various stages testing and development, and over 95% of them are being studied by small pharmaceutical companies. According to the World Health Organization, there are not enough drugs in development to deal with the spread of antibiotic resistance.
Researchers are turning towards solutions that don't involve new antibiotics — but rather use existing drugs in new ways. Hirsch said that in serious cases, doctors may try a specific combination of antibiotics instead of a single drug.
In Slusky's lab, they design proteins that can disable antibiotic resistance by targeting what are called efflux pumps embedded in a bacterium's cell membrane. These pumps do exactly that: they pump out harmful invaders — like from an antibiotic drug — before the drug can take effect. So, if researchers can develop a molecule that inhibits these pumps, then the antibiotic can enter and kill the pathogen.
Slusky says that this is an ongoing area of research, but hopes it's not insurmountable. "Their superpower is that they can evolve super quickly but our superpower is that we can come up with ways to stop them."
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