Substances that slow down the growth and reproduction of bacteria or kill them. It can be created by fungi or similar microorganisms, or it can be produced artificially.
Medicines have been used to combat infections in different ways throughout history, but penicillin was the first antibiotic discovered by Alexander Fleming in 1928.
Table of contents
Antibiotics according to their potency:
Antibiotics are divided into two according to their potency:
- Bacteriostatic antibiotics : Antibiotics that slow the growth of bacteria and stop their reproduction
- Bactericidal antibiotics : Antibiotics that kill bacteria.
A bactericidal effect can be achieved by using some of the bacteriostatic drugs together. Likewise, bactericidal drugs can have a bacteriostatic effect when used at low concentrations.
Erythromycin, clindamycin, tetracycline, sulfonamides, trimethoprim are examples of bacteriostatic antibiotics.
Drugs such as aminoglycosides, vancomycin, penicillins, quinolones, rifampicin, metronidazole are examples of bactericidal antibiotics.
Bacteriostatic antibiotics slow down the growth of bacteria and stop their reproduction. The body’s defense system then destroys the bacteria. Therefore, a strong immune system is needed. However, people with weakened immune systems need bactericidal antibiotics that kill bacteria directly.
Antibiotics by spectrum of action:
Antibiotics are divided into two groups according to the number of bacteria they kill:
- Narrow-spectrum antibiotics : These are antibiotics that are effective only on one or a few types of bacteria. Sometimes, double or triple antibiotic therapy can be applied to provide a wider spectrum of action. For example, penicillin G.
- Broad-spectrum antibiotics: They are powerful antibiotics that are effective on many types of bacteria. For example, tetracyclines, quinolones.
The spectrum of action of antibiotics can be determined by the disc diffusion test, and for some by the antibiogram test.
In the case of an infection, it may make sense to choose an antibiotic with a broad spectrum of action. However, this may lead to unnecessary use of antibiotics and the development of antibiotic resistance. For example, for a simple skin infection, the use of an antibiotic that is necessary for a hospital infection, for which there is no alternative, will increase resistance.
Ways of action of antibiotics:
Antibiotics kill bacteria or stop their growth in different ways.
- Disrupts cell wall synthesis: Bacteria have a hard wall around them. This wall protects against dangers that may come from outside during the high pressure that occurs inside the bacteria due to the food they take from outside. Without this wall, high pressure can easily break up bacteria. Some antibiotics disrupt the structure of this wall and the bacteria swell and break down due to the high pressure. Penicillins, cephalosporins act in this way.
- It impairs cell membrane permeability: The cell membrane of bacteria contains few holes. It has low water permeability and high oil content. Thanks to this oil permeability feature, some antibiotics adhere to the cell membrane. It inhibits enzyme synthesis from the cell membrane and kills the bacteria. Polymyxin, amphotericin, nystatin act in this way.
- Disrupts nucleic acid synthesis: Some antibiotics, such as rifampicin, act by disrupting bacterial DNA and mRNA synthesis. It can have many side effects.
- Disrupts intermediate metabolism : Some antibiotics, such as sulfonamides and trimethoprim, act by disrupting the synthesis of intermediates that allow bacteria to function.
- Disrupts protein synthesis : Some antibiotics such as tetracycline and macrolides also act by disrupting the protein synthesis metabolism of bacteria.
Antibiotics according to their chemical structure :
- Beta lactams,
- Penicillins
- Cephalosporins (1st, 2nd and 3rd generation cephalosporins),
- Monobactams (astreonam),
- Carbapenems (imipenem, meropenem, ertapenem)
- Glycopeptide antibiotics (vancomycin, teicolanin),
- Polymyxins,
- Aminoglycosides (Streptomycin, neomycin, kanamycin, gentamicin, tobramycin, sisomycin, amikacin, netilmicin, isepamycin),
- Tetracyclines (doxycycline, tetracycline, chlortetracycline, metacycline etc.),
- Chloamphenicol,
- Macrolides (erythromycin, spiramycin, clarithromycin, azithromycin etc.),
- Lincosamides (clindamycin),
- Quinolones (ciprofloxacin, ofloxacin, norfloxacin, nalidixic acid etc.),
- rifamycins,
- Nitroimidozoles (metranidazole, ornidazole, tinidazole, nimorazole, secnidazole),
- Sulfonamides (trimethoprimsulfomethoxazole, sulfadiazine etc.),
- Antituberculosis antibiotics (Isoniazid, ethambutol, streptomycin, rifampicin, pyrazinamide, PAS, ethionamide etc.)