Antimicrobial Resistance

Antimicrobial resistance (AMR) occurs when bacteria, viruses, fungi or parasites evolve so that drugs that once killed them no longer work. It is one of the main threats to global health, because it makes infections harder to treat and routine surgery and cancer care riskier.

Resistance arises by mutation and is then selected when a drug is present, a clear case of natural selection. Bacteria resist antibiotics in several ways: enzymes such as beta-lactamases destroy the drug, changes in the target prevent binding, pumps push the drug out and reduced uptake keeps it from entering. Many Gram-negative bacteria combine several of these.

Resistance genes often sit on plasmids, small DNA circles that bacteria exchange by horizontal gene transfer, so a gene can pass between species. Antibiotic use in people and in farm animals, poor sanitation and travel all drive the spread. Well-known examples include MRSA, methicillin-resistant Staphylococcus aureus, and carbapenem-resistant Klebsiella and Escherichia coli.

A 2022 analysis in The Lancet estimated that resistant bacterial infections were directly responsible for about 1.27 million deaths in 2019 and were associated with nearly 5 million. Responses include careful prescribing, better hygiene, vaccines, new antibiotics and diagnostics, and renewed interest in viruses that kill bacteria, as described in bacteriophage. It is a central topic in public health.

• Bacteria — the main organisms involved
• Horizontal Gene Transfer — how resistance genes spread
• Public Health — the field that responds