Antibiotics are medications used to treat infectious bacterial disease. They can either kill the bacteria (bactericidal) or inhibit their growth (bacteriostatic). They have no effect on infections caused by viruses (e.g. a cold or the flu) but they can be presecribed to treat concomitant bacterial infections.
Antibiotics exploit characteristics that are typical of bacteria. For example, they target structures or mechanism in the bacterial cells that are not present in other lifeforms, making them more or less well tolerated by humans and animals. Bacteria have, for example, a cell wall made up of murein or peptidoglycan, a molecule that is only present in bacteria. They also use different structures and enzymes to humans and animals to manufacture proteins and replicate their hereditary material.
Some antibiotics target the construction of new bacterial cell wall components while others interrupt metabolic processes or the replication of hereditary material.
There are about 15 different antibiotic groups that differ in their chemical structure and mode of action and thus also in their efficacy against certain pathogens