Antibiotics (antimicrobials) is a group of drugs that treat infectious diseases that are caused by bacteria. Viral diseases, contrary to widespread belief, are not treated with antibiotics.

Antibiotics either lead to the death of microbes and bacteria, or prevent their reproduction. Antibiotics are distinguished by the use of basic groups, each of which is most effective against certain types of bacteria. The choice of this or that antibiotic is determined by the doctor on the basis of the alleged causative agent of the disease. The first antibiotic was penicillin, a substance isolated from a colony of mold.

There are two main types of action of antibiotics on bacteria: bactericidal and bacteriostatic. Antibiotics with bactericidal effect lead the bacteria to death. Antibiotics with a bacteriostatic effect do not allow bacteria to multiply. Any group of antibiotics is effective against different types of bacteria, which is associated with certain mechanisms of action of these drugs. There are the most common groups of antibiotics and diseases in which they must be used.

Antibiotics are a group of natural or semi-synthetic organic substances capable of destroying microbes or suppressing their reproduction. At the moment, there are many different types of antibiotics with different properties. Knowledge of these properties is the basis of proper antibiotic treatment. The individual qualities and action of the antibiotic mainly depends on its chemical structure. In this article we will talk about the most famous groups of antibiotics, show the mechanism of their work, the spectrum of action, the possibilities of application for the treatment of various infections.

Groups of Antibiotics

Antibiotics are substances of natural or semi-synthetic origin. Antibiotics are obtained by extracting them from colonies of fungi, bacteria, plant tissues or animals. In some cases, the original molecule is subjected to further chemical modifications in order to improve certain properties of the antibiotic (semi-synthetic antibiotics).

At the moment there is a huge number of all kinds of antibiotics. However, in medicine it is used only a few of them, while others, due to increased toxicity can not be used for the treatment of infectious diseases in humans. An extraordinary variety of antibiotics caused the classification and separation of antibiotics into groups. At the same time, antibiotics with a similar chemical structure (derived from the same raw material molecule) and action are collected within the group.

Below we will consider the main groups of antibiotics known to date:

Beta-lactam Antibiotics

The group of beta-lactam antibiotics includes two large subgroups of the most famous antibiotics: penicillins and cephalosporins having a similar chemical structure.

A Group of Penicillins

Penicillins are obtained from the colonies of the mold fungus Penicillium from which the name of this group of antibiotics originates. The main effect of penicillins is related to their ability to inhibit the formation of the bacterial cell wall and thereby suppress their growth and reproduction. During the period of active reproduction, many types of bacteria are very sensitive to penicillin and therefore the action of penicillins is bactericidal.

An important and useful property of penicillins is their ability to penetrate into the cells of our body. This property of penicillins allows treating infectious diseases, the causative agent of which “hides” inside the cells of our body (for example, gonorrhea). Antibiotics from the penicillin group have increased selectivity and therefore practically do not affect the body of the person taking the treatment.

The shortcomings of penicillins include their rapid elimination from the body and the development of resistance of bacteria in relation to this class of antibiotics.

Biosynthetic penicillins are obtained directly from the colonies of mold fungi. The most known biosynthetic penicillins are benzylpenicillin and phenoxymethylpenicillin. These antibiotics are used to treat sore throats, scarlet fever, pneumonia, wound infections, gonorrhea, syphilis.

Semisynthetic penicillins are obtained on the basis of biosynthetic penicillins of the attachment routes of various chemical groups. At the moment there is a large number of semisynthetic penicillins: amoxicillin, ampicillin, carbenicillin, azlocillin.

An important advantage of some antibiotics from the group of semisynthetic penicillins is their activity in relation to penicillin-resistant bacteria (bacteria that destroy biosynthetic penicillins). Due to this semi-synthetic penicillins have a broader spectrum of action and therefore can be used in the treatment of a wide variety of bacterial infections.

The main adverse reactions associated with the use of penicillins are allergic and sometimes are the reason for not using these drugs.

Group of Cephalosporins

Cephalosporins also belong to the group of beta-lactam antibiotics and have a structure similar to that of penicillins. For this reason, some side effects of their two groups of antibiotics coincide (allergy).

Cephalosporins are highly active against a wide range of different microbes and are therefore used in the treatment of many infectious diseases. An important advantage of antibiotics from the group of cephalosporins is their activity against microbes resistant to the action of penicillins (penicillin-resistant bacteria).
There are several generations of cephalosporins:
Cephalosporins of the first generation (cephalothin, cephalexin, cefazolin) are active against a large number of bacteria and are used to treat various infections of the respiratory tract, urinary system, for the prevention of postoperative complications. Antibiotics of this group, as a rule, are well tolerated and do not cause serious adverse reactions.

Cephalosporins of the second generation (Cefomandol, Cefuroxime) are highly active against bacteria that inhabit the gastrointestinal tract, and therefore can be used to treat various intestinal infections. Also, these antibiotics are used to treat infections of the respiratory and bile ducts. The main side reactions are associated with the occurrence of allergies and disorders of the gastrointestinal tract.

Cephalosporins of the third generation (Cefoperazone, Cefotaxime, Ceftriaxone) are new drugs that have high activity against a wide range of bacteria. The advantage of these drugs is their activity against bacteria, insensitive to the effects of other cephalosporins or penicillins and the ability to prolong the delay in the body. These antibiotics are used to treat severe infections that are not treatable by other antibiotics. Side effects of this group of antibiotics are associated with a violation of the composition of the intestinal microflora or the occurrence of allergic reactions.

Antibiotics from the Group of Macrolides

Macrolides are a group of antibiotics with a complex cyclic structure. The most famous representatives of antibiotics from the macrolide group are Erythromycin, Azithromycin, Roxithromycin.

The action of macrolide antibiotics on bacteriostatic bacteria – antibiotics block bacteria structures that synthesize proteins, resulting in microbes losing the ability to multiply and grow.

Macrolides are active against many bacteria, but the most remarkable property of macrolides is perhaps their ability to penetrate the cells of our body and destroy microbes that do not have a cell wall. Such microbes include chlamydia and rickettsia – pathogens of atypical pneumonia, urogenital chlamydia and other diseases that can not be treated with other antibiotics.

Another important feature of macrolides is their relative safety and the possibility of long-term treatment, although modern macrolide treatment programs provide for ultra-short courses lasting three days.

The main areas of use of macrolides are the treatment of infections caused by intracellular parasites, the treatment of patients with allergies to penicillins and cephalosporins, the treatment of young children, pregnant women and nursing mothers.

Antibiotics from the group of tetracyclines

The most known antibiotics from the group of tetracyclines are Tetracycline, Doxycycline, Oxytetracycline, Metacyclin. The action of antibiotics from the tetracycline group is bacteriostatic. Like macrolides, tetracyclines are able to block protein synthesis in bacterial cells; however, unlike macrolides, tetracyclines have less selectivity and therefore inhibit the synthesis of proteins in the cells of the human body in large doses or with prolonged treatment. At the same time, tetracyclines remain indispensable “helpers” in the treatment of many infections. The main areas of use of antibiotics from the group of tetracyclines are treatment of infections of the respiratory and urinary tract, treatment of severe infections such as anthrax, tularemia, brucellosis,

Despite the relative safety, with prolonged use, tetracyclines can cause serious side effects: hepatitis, skeletal and dental lesions (tetracyclines are contraindicated in children under 14 years of age), malformations (contraindication for use during pregnancy), allergies.

Widespread use of ointments containing tetracycline. Applied for local treatment of bacterial infections of the skin and mucous membranes.

Antibiotics from the group of aminoglycosides

Aminoglycosides are a group of antibiotics, which include such drugs as Gentamicin, Monomycin, Streptomycin, Neomycin. The spectrum of action of aminoglycosides is extremely wide and includes even pathogens of tuberculosis (Streptomycin).

Aminoglycosides are used to treat severe infectious processes associated with a massive spread of infection: sepsis (blood poisoning), peritonitis. Also, Aminoglycosides are used for local treatment of wounds and burns.

The main disadvantage of aminoglycosides is their high toxicity. Antibiotics from this group have nephrotoxicity (kidney damage), hepatotoxicity (liver damage), ototoxicity (can cause deafness). For this reason, aminoglycosides should be used only for life indications, when they are the only treatment option and can not be replaced by other drugs.


Levomycetin (Chloramphenicol) inhibits the synthesis of bacterial proteins, and in large doses causes a bactericidal effect. Levomycetin has a wide range of effects, but its use is limited because of the risk of serious complications. The greatest danger associated with the use of the antibiotic Chloramphenicol is in the defeat of the bone marrow, which produces blood cells.

Antifungal Antibiotics

Antifungal antibiotics are a group of chemicals capable of destroying the membrane of cells of microscopic fungi, causing their death.

The most famous representatives of this group are the antibiotics Nystatin, Natamycin, Levorin. The use of these drugs in our time is markedly limited due to low efficiency and a high incidence of side effects. Antifungal antibiotics are gradually being replaced by highly effective synthetic antifungal agents.

Leave a Comment