Antibiotic resistance occurs when bacteria evolve mechanisms that protect them from drugs designed to kill them or stop their growth. This happens mainly through genetic changes. Spontaneous mutations can alter antibiotic targets, reduce drug uptake, or increase efflux pumps that expel antibiotics from the cell. Bacteria also share resistance genes through horizontal gene transfer, using plasmids, viruses, or direct cell contact, allowing resistance to spread rapidly between different strains and species.

Several factors accelerate resistance. Overuse and misuse of antibiotics in human medicine, such as prescribing them for viral infections or not completing a full treatment course, expose bacteria to drug levels that encourage survival of resistant variants. In agriculture and livestock, routine antibiotic use for growth promotion or disease prevention creates large reservoirs of resistant bacteria that can reach humans through food, water, and the environment. Poor sanitation, crowded healthcare settings, and global travel help resistant strains spread worldwide.

The consequences are serious. Common infections become harder to treat, requiring more expensive or toxic drugs and longer hospital stays. Medical procedures that rely on effective antibiotics, such as surgeries, cancer chemotherapy, and care for premature infants, become riskier. Some “superbugs” are resistant to multiple antibiotic classes, leaving few or no effective treatments.

Addressing antibiotic resistance requires coordinated actions. These include using antibiotics only when necessary, improving diagnostics to distinguish bacterial from viral infections, strengthening infection prevention and control, monitoring resistance patterns, reducing nonessential antibiotic use in animals, and investing in new antibiotics, vaccines, and alternative therapies such as phage treatment.