Antimicrobial resistance

Antimicrobial resistance is the ability of a microorganism to survive or continue multiplying despite a medicine that would normally control it. The term covers resistance in bacteria, viruses, fungi and parasites. Antibiotic resistance is one important part of AMR, but the terms are not interchangeable: antibiotics act on bacteria, while other antimicrobial medicines target different kinds of infectious organisms. Resistance belongs to the microbe, not to the person taking a medicine. An infection may become more difficult to treat when its causative organism is resistant, although resistance to one drug does not necessarily mean that every treatment will fail.

Resistance is a natural biological process, but antimicrobial exposure can accelerate its selection. A medicine may suppress susceptible microbes while resistant ones survive and reproduce; resistance traits can also pass between microbes, especially bacteria. The more resistant organisms circulate, the harder infections can be to prevent and treat. Inappropriate or excessive use of antimicrobials is one driver, but the wider conditions matter too: gaps in vaccination, diagnosis, clean water, sanitation and infection control can increase infections and the need for treatment, or allow resistant organisms to spread. Movement between people, animals, food systems and the environment makes this a cross-sector problem.

Drug-resistant infections can require different or longer courses of treatment, extend hospital stays and leave clinicians with fewer effective options. They can also make procedures that depend on infection control—such as surgery, cancer treatment and organ transplantation—riskier. AMR affects more than human medicine: resistant infections can affect animals and plants, while antimicrobial residues and resistant microbes in the environment are also concerns. The scale is difficult to summarize with a single number because surveillance systems measure particular organisms, medicines and infections. WHO reported that approximately one in six laboratory-confirmed bacterial infections worldwide was resistant to antibiotics in 2023; this figure concerns bacterial infections in the available data, not every form of AMR.

Reducing AMR requires both slowing the emergence of resistance and preventing resistant infections from spreading. Measures include using antimicrobial medicines only when appropriate and according to professional guidance; improving vaccination, hygiene and infection prevention; ensuring access to clean water and sanitation; and strengthening diagnostic laboratories and surveillance. WHO’s Global Antimicrobial Resistance and Use Surveillance System (GLASS) helps countries collect comparable information to guide public-health action. Its 2025 global antibiotic-resistance report analyzed more than 23 million confirmed infection cases reported by 104 countries for 2023, illustrating both the value of shared monitoring and the importance of the data coverage behind global estimates.

AMR is often approached through One Health: coordinated work across human, animal and plant health and the environment. Antimicrobial use in health care and agriculture, infection control, food systems, waste management and environmental pollution can interact, so action in only one sector is insufficient. International agencies emphasize prevention, responsible use, surveillance and research across these connected settings. The framework also reflects an important distinction: resistant infections are a biological problem, but their scale and effects are shaped by access to health care, sanitation, medicines and effective public-health systems.