Antimicrobial resistance

Antimicrobial resistance (AMR) happens when microbes evolve defenses against the drugs—called antimicrobials—used to treat infections in people, animals, and plants. Any microbe can become resistant: bacteria (leading to antibiotic resistance), viruses (antiviral resistance), parasites (antiparasitic resistance), and fungi (antifungal resistance). These adaptations are all part of AMR, which creates problems for every country and every age group. The main drivers are misuse and poor management of antimicrobials, though resistance can also arise naturally through genetic mutations and the spread of resistance genes.

Microbes that resist multiple drugs are called multidrug-resistant (MDR) and are sometimes referred to as superbugs. Antibiotic resistance is a serious part of AMR. It develops through spontaneous mutations, horizontal gene transfer, and increased selective pressure from overusing antibiotics in medicine and agriculture, which speeds up resistance.

Overview

Preventive steps—like using narrow-spectrum antibiotics and improving hygiene—aim to slow its spread. The World Health Organization (WHO) says AMR is one of the top global public health and development threats. It estimates that bacterial AMR directly caused 1.27 million deaths worldwide in 2019 and contributed to over 4 million deaths in 2021. The overall burden is huge, with nearly 5 million annual deaths linked to resistant infections.

Infections from AMR microbes are harder to treat and often need expensive alternative therapies that may have worse side effects. The WHO and other international bodies warn that without action, AMR could cause up to 10 million deaths per year by 2050. Global efforts, including calls for international AMR treaties, focus on coordinated action to limit misuse, fund research, and ensure access to necessary antimicrobials in developing countries. However, the COVID-19 pandemic diverted resources and scientific attention away from AMR, making the problem worse.

Definition

In 2026, Israeli scientists announced the discovery of bacteria that can create dozens of copies of genes that help them survive antibiotics. Antimicrobial resistance means a microorganism is resistant to an antimicrobial drug that once could treat an infection caused by that microbe. Resistance is a property of the microbe, not of the person or organism it infects.

All types of microbes can develop drug resistance, so there are antibiotic, antifungal, antiviral, and antiparasitic resistance. Antibiotic resistance is a subset of AMR, linked specifically to bacteria. It breaks down into two further types: microbiological and clinical. Microbiological resistance is the most common and comes from genes—either mutated or inherited—that let bacteria resist the mechanism an antibiotic uses to kill them.

Clinical resistance shows up when normally susceptible bacteria survive treatment, causing therapy to fail. In both types of acquired resistance, bacteria can pass the genetic cause to others through horizontal gene transfer: conjugation, transduction, or transformation. This lets resistance spread within the same pathogen species or even to similar bacterial pathogens. A 2014 WHO report stated, "this serious threat is no longer a prediction for the future, it is happening right now in every region of the world and has the potential to affect anyone, of any age, in any country.

Antibiotic resistance—when bacteria change so antibiotics no longer work in people who need them to treat infections—is now a major threat to public health." In 2024, nearly 5 million deaths were associated with AMR, and deaths directly attributable to AMR numbered 1.27 million. One in five people who died due to AMR were children under five years old. In 2018, the WHO considered antibiotic resistance one of the biggest threats to global health, food security, and development. Deaths from AMR vary by region.

The European Centre for Disease Prevention and Control calculated that in 2015 there were 671,689 infections in the EU and European Economic Area caused by antibiotic-resistant bacteria, resulting in 33,110 deaths. Most were acquired in healthcare settings. In 2019, there were 133,000 deaths caused by AMR.

Causes

AMR is driven largely by the misuse and overuse of antimicrobials. Microbes reproduce and spread quickly, and they can adapt to their environment and change how well they survive. At the same time, many people lack access to essential antimicrobials. This leads to microbes either evolving defenses against the drugs used to treat them, or certain strains that already have natural resistance becoming much more common than those that do not.