Two of the first antimicrobials developed were sulfonamides and penicillin (PCN). Sulfonamides are bacteriostatic, which means they stop the growth of bacteria, but do not kill bacteria. Penicillin, the first antibiotic, is a bacteriocidal and kills bacteria using lysis, which explodes the bacteria into parts.
Tip: A static means stops growth while cidal (homicide) means kills.
Today there are many synthetic and semi-synthetic antimicrobials on the market that stop some bacteria from growing and kill other bacteria. For example, chloramphenicol is bacteriostatic and stops most bacteria from growing while it is bacteriocidal and kills S pneumoniae and H influenza in cerebral spinal fluid. Tetracycline is also bacteriostatic and bacteriocidal; in small concentrations it stops the growth of bacteria and in high concentration it kills bacteria.
Sulfonamides and penicillin are administered orally, topically as an ointment or cream, or parenterally and are absorbed into the body and distributed by the circulatory system. In severe infections, they can be administered directly at the site of the infection such as in the eye or rubbed on the skin.
There are four ways in which these medications work.
1. They inhibit the bacteria from growing a cell wall (cell wall synthesis).
2. They disrupt or alter the permeability of the bacteria's membrane. The membrane is within the cell wall and is used to let nutrients into the cell and send waste out of the cell.
3. They inhibit the bacteria's ability to make protein (protein synthesis). Medications that stop the growth of bacteria interrupt steps in protein synthesis. Those that kill bacteria cause the bacteria to form defective proteins.
4. They inhibit the bacteria's capability to make (synthesize) essential metabolites. A metabolite is a component necessary for bacteria's metabolism to function properly.
Medication used to stop the growth of microbials or kill them outright have side effects, some of which can adversely affect the patient. Some cause an allergic reaction while others lead to an exaggerated immune response. Here are a few common ones that you probably recognize:
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