The ability of an organism to withstand the effects of antibiotics, often conferred by plasmids.Antibiotic resistance is the ability of bacteria and other microorganisms to survive and grow in the presence of antibiotics that would normally kill them or inhibit their growth. This resistance can be intrinsic or acquired, and it is a major global health concern because it makes infections harder to treat, leading to longer illnesses, higher medical costs, and increased mortality. The spread of resistance genes, often carried on plasmids, can occur between different bacterial species, accelerating the problem.
The phenomenon was recognized soon after the introduction of penicillin in the 1940s, with the first reports of resistant strains appearing in the 1950s. The term 'antibiotic resistance' became widely used as the problem grew.
Resistance mechanisms include enzymatic inactivation of the antibiotic, alteration of the drug's target site, reduced permeability of the cell membrane, and active efflux pumps that expel the drug. Plasmids are small, circular DNA molecules that can replicate independently and be transferred between bacteria via conjugation, transformation, or transduction. They often carry multiple resistance genes, allowing bacteria to become resistant to several antibiotics at once.
Understanding resistance is essential for developing new antibiotics, designing combination therapies, and implementing stewardship programs to preserve the effectiveness of existing drugs.
Some bacteria can become resistant to antibiotics by acquiring genes from completely unrelated species, even from bacteria that produce the antibiotics themselves.












