Antibiotics are those antimicrobial agents that prevent the growth of bacterial infection within the human body. Antibiotics perform a systematic way to prevent bacterial growth. This systematic way of antibiotics is called the mechanism of action. Based on the antibiotics’ mechanism of action, there are several types of antibiotics present in the market. However, on the basis of action, antibiotics are categorised into two groups. Bactericidal antibiotics are the antibiotics that focus on killing the bacteria before it spreads within the body, and bacteriostatic antibiotics are the antibiotics that focus on limiting or inhibiting the growth of the bacteria.

What are Antibiotics?

Antibiotics are antibacterial or anti-microbial substances that are effective against bacteria. These are the active agents that fight against the bacteria, either by killing them or inhibiting the growth of these bacteria. Antibiotic medicines are being widely used in the pharmaceutical industries to fight against bacterial infections. Antibiotics must not be confused with anti-viral, as these antibiotics are ineffective against viruses like the common cold, influenza, etc. There are a number of antibiotics present in the market, but most of the renowned antibiotics are Penicillin, Macrolides, Cephalosporins, Sulfonamides, etc. However, the antibiotics are classified on the basis of their action into two groups, Bactericidal antibiotics and Bacteriostatic antibiotics.

Antibiotics Mechanism of Action:

The antibiotics follow a specific way of killing or limiting the growth of the bacteria, the process by which antibiotics stop the bacterial infection from spreading is known as the mechanism of action. The antibiotic mechanism of action depends on different types of antibiotics. Antibiotics’ mechanism of action determines the toxicity of the antibiotics to stop or kill the bacteria of the same toxicity. The mechanism of action of antimicrobial agents must be determined in such a way so that it does not cause any effect on the organisms.

Mode of Action of Antibiotics:

The mode of action of antibiotics can be categorised into several groups, and these antibiotics are classified under the basis of the mode of action. The different mechanisms of action of antimicrobial agents are:

• Inhibition of microbial cell wall synthesis: The basic principle of these antibiotic inhibitors is to stop or block the peptidoglycan synthesis within the cell wall so as to prevent the production of the cell wall. The cell wall is the most important feature of the bacteria, which maintains its shape and strength.
• Inhibition of DNA synthesis: Deoxyribonucleic acid (DNA) is the basic component of the chromosome of any bacterial cell, which controls the activity of the cell. The antibiotics that inhibit the DNA synthesis directly attack the bacteria’s DNA and interfere with the transcription by blocking the DNA gyrase enzyme to stop the formation of the DNA.
• Inhibition of protein synthesis: The bacteria cell is composed of ribosomes, which are very important for protein synthesis. The inhibitors of protein synthesis attack the ribosome of the bacterial cells to prevent protein synthesis. The basic principle of working these antibiotics is to bind the receptors on either the 30S or 50S subunit of the ribosomes. As there will be no receptions, there will be no synthesis of protein in the bacterial cell, which will cause them to be extinct.
• Inhibition of metabolic pathway: The antibiotics that inhibit the metabolic pathways are called anti-metabolites. The basic principle of these antibiotics is to block the folate (folic acid) synthesis, which are essential for producing the DNA and RNA of bacteria.

Examples of Antibiotics based on mode of action:

• Cell wall synthesis inhibitor: Penicillin is one of the basic examples of cell wall inhibitor antibiotics. Penicillin’s mechanism of action depends basically on affecting or inhibiting the final crosslink of the bacteria.
• DNA synthesis inhibitor: One such example of a DNA synthesis inhibitor is Fluoroquinolones. The Fluoroquinolones’ mechanism of action is to prevent the DNA synthesis of bacteria by transcription of two particular enzymes within the bacterial cell. The enzymes are DNA gyrase and topoisomerase IV enzymes which are essential for bacterial DNA synthesis. The blockage of these enzymes leads to the breakage of the DNA structure and the death of the bacteria.
• Protein synthesis inhibitor: Macrolides’ mechanism of action works as the protein synthesis inhibitors on the 50S subunit of the ribosome. The macrolides’ mechanism of action is to prevent the peptidyl transferase from synthesising with the growing peptides which are attached to the tRNA. This prevents bacterial ribosomal reception. Thus, putting a limitation on the protein synthesis within the bacterial cell.
• Metabolic pathway inhibitor: Sulfonamides are an example of metabolic pathway inhibitors. It is a broad-spectrum antibiotic that inhibits folate synthesis by preventing the addition of Para-aminobenzoic acid (PABA) into the folic acid.

Conclusion:

Antibiotics are antimicrobial agents that prevent bacterial growth. It mainly focuses on either killing the bacteria or preventing the growth of the bacteria. On the basis of their action, antibiotics are categorised into two groups, bactericidal antibiotics and bacteriostatic antibiotics. Antibiotics perform a specific way of killing the bacteria, which are called the mechanism of action. The antibiotic mechanism of action categorises these antimicrobial agents into several groups. Penicillin, macrolides, Cephalosporin, etc., are various types of antibiotics. To better understand the concept of antibiotics, one is required to gain knowledge about the working of several antibiotics.