Overview
Antimicrobial resistance refers to microorganisms no longer responding to antimicrobial medicine such as antibiotics. This is a natural phenomenon that occurs over time through genetic changes in the microorganisms.
AMR is strongly accelerated by inappropriate use of antimicrobial medicine. AMR happens when microorganisms such as bacteria, fungi, viruses and parasites become resistant to antimicrobial medicines such as antibiotics, antifungals, antivirals and antiparasitics. As a result, these medicines become ineffective, and infections become difficult to treat.
Without effective antimicrobials for prevention and treatment of infections, medical procedures such as organ transplantation, caesarean sections, cancer chemotherapy and diabetes management become challenging.
Microorganisms that develop resistance to antimicrobials are sometimes referred to as “superbugs”.
AMR is a global concern
New resistance mechanisms are emerging and spreading globally, threatening our ability to treat common infectious diseases and resulting in prolonged illness, disability and death.
AMR is a threat for all countries globally, independent of income levels. It poses a threat to global health, food security and achieving the 2030 Sustainable Development Goals.
AMR has strong economic costs for health-care systems and national economies. In health-care systems, costs increase for example due to lengthier stays in hospitals, the requirement of more intensive care, and the need to use more expensive alternative treatments.
AMR also has significant implications for the health of animals and plants. Animal health, human health and environmental health are intrinsically intertwined and interdependent. Resistant bacteria can spread between and within animal, human and plant populations and travel through the waterways, soil and air, also infecting wild animals along the way. As more than 60% of emerging pathogens that cause human diseases originate from animals, protecting the health of animals and the environment protects human health.
Emergence and spread of AMR
AMR occurs naturally over time, usually through genetic changes. However, the inappropriate use of antimicrobials is accelerating this process.
Antimicrobial medicines are often used inappropriately in humans, animals and on crops. As an example, antibiotics should not be used against viral infections such as colds and influenza, but they often are.
Drug-resistant microbes are found in humans, animals, food and the environment. They can spread from person to person, and between people, animals and the environment, emphasizing the need to use a One Health approach that recognizes the interlinkages between human, animal and environmental health.
Antibiotics that are critical to human medicine should be used prudently in veterinary and agricultural sectors. Still, they are often used as growth promoters for animals and fish in many countries around the world.
The spread of AMR can be controlled by:
- strong infection prevention and control including routine vaccinations;
- stewardship programmes providing relevant training and support for medical staff to follow evidence-based guidelines for prescribing and administering antibiotics, and to use diagnostic tests to ensure targeted treatment;
- prudent use of antibiotics in agriculture and food production.
Resistance in bacteria
The spread of drug-resistant bacteria challenges antibiotic treatments for widespread bacterial infections. Patients with infections caused by drug-resistant bacteria are at increased risk of worse clinical outcomes or even death. Treatment of drug-resistant bacteria is more resource intensive and leads to increased health-care costs.
Below are a few examples of drug-resistance in bacteria that are of concern:
- In Klebsiella pneumoniae, a common intestinal bacterium that can cause life-threatening infections, resistance to a last-resort treatment (carbapenem antibiotics) has spread to all regions of the world. K. pneumoniae is now a major cause of hospital-acquired infections such as pneumonia, bloodstream infections and infections in newborns and intensive-care unit patients. In some countries in the European Region, antibiotics stopped working in more than half of people treated for K. pneumoniae infections due to resistance.
- In Escherichia coli, a bacteria that can cause urinary tract infections, resistance to one of the most widely used medicines (fluoroquinolone antibiotics) has developed. In many countries in the European Region this treatment is now ineffective in more than half of patients.
- In Staphylococcus aureus, a bacteria and common cause of severe infections in health facilities and communities, resistance to first-line drugs is on the return in some parts of the Region, while it remains widespread in other parts. Infections with methicillin-resistant Staphylococcus aureus (MRSA) continue to be important in the Region, with levels remaining high in several countries and combined resistance to another antimicrobial group quite common.
- In Enterobacteriaceae bacteria, resistance against the last-resort treatment for life-threatening infections, colistin, has spread to several countries and regions. This means that infections caused by such drug-resistant bacteria are now untreatable.
Resistance in tuberculosis (TB)
Drug-resistant tuberculosis (DR-TB) remains a significant public health threat in the European Region, with the vast majority of cases concentrated in eastern Europe and central Asia. In 2022, 32 000 new cases of rifampicin- or multidrug-resistant TB (RR/MDR-TB) were reported in the Region. It is estimated that 1 in 4 new TB patients and half of previously treated patients have RR/MDR-TB, the highest proportion globally.
To address this challenge, national TB programmes in most high-burden countries in the Region have fully transitioned to using new WHO-recommended medications for DR-TB treatment. These new treatments have significantly improved effectiveness and safety while reducing the treatment duration from 20 months to just 6–9 months and are fully oral.
From 2020 to 2023, 13 countries in eastern Europe and central Asia collaborated with WHO/Europe to evaluate the outcomes of a modified shorter regimen for MDR-TB in operational research settings. This regional initiative supported the introduction and scale up of new TB medicines in line with the latest WHO guidelines, achieving a treatment success rate of 83% and a recurrence probability of just 1% after 12 months (as reported in The Lancet).
Resistance in HIV
HIV drug resistance is caused by changes in the genetic structure of HIV that affect the ability of medicines to block the replication of the virus. As for other pathogens that no longer respond to antimicrobial medicine, the increased use of HIV medicines has been accompanied by the emergence of HIV drug resistance, the levels of which have steadily increased in recent years.
The adoption of antiretroviral therapy (ART) has significantly increased over the past decade, saving the lives of tens of millions of people living with HIV worldwide. As of 2023, more than 60% of people living with HIV in the European Region were receiving ART. While we are still far from the universal ART coverage we aim for, this is a significant increase from 35% in 2010. However, the increased use of ART has been accompanied by a concerning rise in HIV drug resistance, which has been steadily growing in recent years.
All antiretroviral drugs, including those from newer classes, are prone to becoming partially or fully ineffective due to drug-resistant viral strains. For example, even for dolutegravir – one of the most widely used antiretrovirals, with a high genetic barrier to resistance development – there are reports of emerging drug resistance. Therefore, it is of particular importance to address HIV drug resistance as yet another example of AMR that can undermine the effectiveness of treatment regimens, leading to more infections and higher rates of HIV-related illness and death.
Resistance in influenza
Antiviral drugs are important for the treatment of epidemic and pandemic influenza. So far, virtually all influenza A viruses circulating in humans are resistant to one category of antiviral drugs – M2 inhibitors (amantadine and rimantadine). However, the frequency of resistance to the neuraminidase inhibitor oseltamivir remains low (1–2%). Antiviral susceptibility is constantly monitored through the WHO Global Influenza Surveillance and Response System.
WHO’s response to AMR
WHO/Europe is supporting countries to address the threat of antimicrobial resistance by:
- providing technical guidance;
- performing national assessments and supporting national action plan development;
- supporting health leadership and regional policy development;
- facilitating intersectoral collaboration;
- providing training and building capacity;
- publishing the latest surveillance data;
- monitoring the implementation of the “Roadmap on antimicrobial resistance for the WHO European Region 2023–2030”; and
- supporting advocacy and public awareness raising.
WHO/Europe works with countries across all topics relevant to AMR, including:
- surveillance of antimicrobial resistance and consumption
- antimicrobial stewardship
- infection, prevention and control
- water, sanitation and hygiene
- awareness and behaviour change
- laboratory quality management
- food safety.