However, antimicrobial agents have now been used so widely that some of the microbes targeted by the drugs have adapted and become resistant to these drugs.
According to the Centers for Disease Control and Prevention (CDC), at least 2 million people become infected with antimicrobial-resistant bacteria in the United States every year. Around 23,000 people die as a result.
In addition, 1 in every 25 hospital patients has a health-associated infection (HAI) on any given day.
Here are some key points about antimicrobial resistance.
- Antimicrobial resistance can develop in bacteria, fungi, parasites, and viruses.
- Resistance can make treating infections a costly, difficult, and prolonged process.
- Prominent forms of antimicrobial-resistant infections include MRSA, tuberculosis, HIV and malaria.
- Antimicrobial drugs must be used exactly as they are prescribed, until the end of the course, or they can contribute toward antimicrobial resistance.
- Not every infection needs to be treated with antimicrobial drugs.
- If antibiotics stop working because of overuse, diseases that have been eradicated may come back.
What is antimicrobial resistance?
Antibiotics and other antimicrobial drugs are crucial for fighting infection and saving lives, but they must be used correctly.
Antimicrobial resistance (AMR), or drug resistance, develops when micro-organisms — bacteria, fungus, parasites or viruses — no longer respond to a drug that used to treat them effectively.
The consequences of AMR include:
- infections that are harder to control and that stay longer inside the body
- longer hospital stays, increasing the economic and social costs of infection
- a higher risk of diseases spreading
- a greater chance of fatality due to infection
A major concern is that AMR could lead to a post-antibiotic era, a time where antibiotics would no longer work.
In this scenario, common infections and minor injuries that became easy to treat in the 20th century could again become fatal.
Antibiotic versus antimicrobial resistance
It is important to distinguish between antibiotic and antimicrobial resistance.
- Antibiotic resistance is the ability of bacteria to resist antibiotics.
- Antimicrobial resistance is resistance from any microbes to the drugs used to kill them.
AMR can develop not only in bacteria but also in fungi, parasites, and viruses. This could affect people with Candida, malaria, HIV, and a wide range of other conditions.
Microbes can become resistant to drugs for both biological and social reasons.
As soon as a new antibiotic is introduced, scientists know there is a good chance that, sooner or later, it will stop being effective. One reason for this is changes occur within the pathogens themselves.
Mutation: When microbes reproduce, genetic mutations can occur. Sometimes, this can lead to the creation of a microbe with genes that help it to survive exposure to antimicrobial agents.
Selective pressure: Microbes that carry resistance genes survive to replicate themselves. The newly generated resistant microbes will eventually become the dominant type.
Gene transfer: Microbes can pick up genes from other microbes. Genes with drug-resistant qualities can easily transfer between microbes.
Phenotypic change: Pathogens can alter components of their makeup to become resistant to the preferred antimicrobial agents
Not following recommendations for the use of some drugs can increase the risk of antimicrobial resistance.
The use of antibiotics by people is an important contributor to AMR.
Inadequate diagnostics: Sometimes a doctor prescribes antimicrobials "just in case," or broad-spectrum antimicrobials are prescribed when a specific drug would be more suitable. These increase the risk of AMR.
Inappropriate use: If a person does not complete course of antimicrobial drugs, some microbes may survive and develop resistance to the drug. Resistance can also develop if drugs are used for conditions they cannot treat, for example, taking an antibiotic for a viral infection.
Agricultural use: Using antibiotics in farm animals can promote drug resistance. Drug-resistant bacteria can be found on meat and in food crops exposed to fertilizer or water that is contaminated with animal feces. This can provide a route for animal-to-human transmission.
Hospital use: Patients who are critically ill often receive high doses of antimicrobials. This factor, combined with being in an environment where various diseases are present, encourages the spread of AMR microbes.
They add that "tens of millions" of prescriptions are given annually for antibiotics that offer no benefit. This increases the risk of the individual developing a resistant infection in the future.
Examples of resistance
Antimicrobial resistance can be found in bacteria, viruses, fungi, and parasites.
Here are some examples:
Tuberculosis (TB): This airborne lung disease, caused by bacterial infection, was a major killer before the advent of antibiotics. Drug-resistant forms of TB have emerged worldwide, however, and these are immune to standard antibiotic treatment.
TB that is not drug resistant requires multidrug treatment daily for 6 to 12 months.
Drug-resistant TB is more complex to treat, requiring taking the drugs for a longer time, and it needs close supervision. Poor management can result in fatalities.
Methicillin-resistant Staphylococcus aureus (MRSA): This potentially fatal bacterial infection is most commonly acquired in hospitals. In the past, it was a well-controlled infection, but it has become a major public health concern, due to antibiotic resistance.
Gonorrhea: Gonorrhea is a sexually transmitted bacterial infection that is common in the U.S. and elsewhere. Recently, drug-resistant forms of this bacterial disease have been reported. Now, only one type of drug remains that is effective against the drug-resistant form of this disease. Drug-resistant gonorrhea is described by the CDC as an "urgent public health threat."
Human immunodeficiency virus (HIV): Effective antiviral treatment is now available for HIV that prevents it from developing to a more serious condition and that can make virus levels undetectable, and therefore not transmissable. If medical costs, for example, deter people from adhering fully to their drug regimen, new, drug-resistant strains of the virus may appear.
Fungal infections: Candida, Aspergillus, and other fungi can a lead to a range of serious infections. Candida albicans is responsible for the common vaginal infection known as thrush. Aspergillosis can cause or worsen a lung condition. Some of these infections can have fatal consequences. There is concern that fungi are increasingly resistant to antimicrobial treatment.
Malaria: This parasitic disease is spread by mosquitoes and kills around 1 million people every year worldwide. In many parts of the world, the evolution of drug-resistant parasites has led to certain antimalarial drugs becoming ineffective.
Treatment and alternatives
As infections stop responding to current drugs, there is an urgent need to find alternatives.
In some cases, this means using combinations of different medicines, known as multiple-drug therapy, as in the treatment of TB.
Scientists are also looking for new forms of treatment, including new types of antibiotics and other alternatives.
What are the alternatives?
A number of novel ways of combatting bacteria have been suggested, for example, for Clostridium difficile (C. difficile).
- using a virus that consumes bacteria, known as a "bacteriophage," in drug form
- using monoclonal antibodies that can combat the effects of the toxins produced
- developing vaccines to prevent infection from occurring
- fecal microbiota transplant
- the use of probiotics to restore the gut flora
More research is needed into these treatments.
Meanwhile, health professionals are urged to use antibiotics only when they are useful and necessary, and patients are asked to use antimicrobial drugs exactly as advised by a health provider, and only after following a complete diagnosis.
Preventing diseases from spreading, for example, through good hygiene, is one way to reduce the need for or use of medications.
Preventing microbes from developing resistance to drugs has become as important as treating them.
The main reason for the increase in AMR appears to be the repeated and improper use of antimicrobials.
Steps that people can take to help lower the risk of AMR include:
- Only using antimicrobial drugs when prescribed by a professional.
- Always completing a course, even if symptoms are gone. If not, the drug may only kill off the most vulnerable microbes, leaving others to survive and develop resistance.
- Never sharing antimicrobials or using drugs left over from other prescriptions. They may not be suitable for different forms of infection.
- Not pressurizing doctors into prescribing antimicrobials when they are not necessary.
- Preventing the spread of microbes with good hygiene, including washing hands thoroughly and ensuring that food preparation areas are clean.
- Getting recommended vaccinations, as this will reduce the risk of needing to take medication in the future.
In 1945, Alexander Fleming warned about antibiotics that "the ignorant man may easily underdose himself and by exposing his microbes to non-lethal quantities of the drug, make them resistant."
In 2014, the WHO echoed these fears in the following words: "Without urgent action we are heading for a post-antibiotic era, in which common infections and minor injuries can once again kill."
Individuals, health workers, policy makers, and industrialists all have a part to play in preventing antibiotic resistance from becoming a global crisis.