Antibiotics are medicines that fight infections caused by bacteria (also called microorganisms). These drugs can kill or prevent bacteria from growing. They can also help the body fight infection and heal after an illness. Antibiotics have saved lives and made some diseases much less serious. Infections that were once common, such as pneumonia and urinary tract infections, are now rare.
Many antibiotics are available in pill form. Others are given as liquid or injection. They can be taken in a doctor’s office or at home. The way an antibiotic works depends on what kind of infection a person has. Some antibiotics, like penicillin, work by entering the bacterial cells and killing them. Others, such as cephalosporins, enter the bacterial cell and block the bacterium’s ability to make a cell wall. Still other antibiotics, such as clindamycin, attack only certain types of bacteria.
If people use antibiotics incorrectly, they may promote the growth of harmful bacteria and cause them to share their resistance properties with other bacteria. This can lead to antibiotic-resistant infections that are difficult or impossible to treat.
The first beta-lactam antibiotic, penicillin, was discovered by chance in a blob of mold that had grown on a petri dish. More recently, antibiotics have been developed using microorganisms that are either naturally produced or made in the laboratory. People need a prescription from a healthcare professional to get most oral antibiotics. This helps ensure that the right antibiotic is used for their infection and that it is administered correctly. It is also important for people to finish the entire course of antibiotic treatment — even if they feel better — to make sure that the infection is completely treated and that resistant bacteria are not formed.