Antimicrobial agents are substances or compounds that are specifically designed to kill or inhibit the growth of microorganisms such as bacteria, viruses, fungi, and parasites. These agents are widely used in the prevention and treatment of infections caused by microorganisms. Antimicrobial agents can be classified into several categories based on their mechanisms of action.

1. Antibiotics: Antibiotics are natural or synthetic compounds that are specifically designed to kill or inhibit the growth of bacteria. They work by interfering with the biosynthesis of essential proteins or the synthesis of the bacterial cell wall.

2. Antivirals: Antivirals are compounds that are specifically designed to target viruses. They work by interfering with the replication of the virus by either inhibiting the viral enzymes or blocking the cellular receptors required for viral entry.

3. Antifungals: Antifungals are used to treat fungal infections. They work by interfering with the synthesis of fungal cell wall or the synthesis of ergosterol, an essential component of the fungal cell membrane.

4. Antiparasitics: Antiparasitics are compounds used to treat infections caused by protozoa, helminths, and ectoparasites. They work by targeting specific enzymes or structures within the parasite, disrupting their essential metabolic processes.

In addition to these classes of antimicrobial agents, there are also several broad-spectrum agents that can target a wide range of microorganisms. These include disinfectants, antiseptics, and sterilizing agents. Disinfectants are used to kill or eliminate microorganisms on non-living surfaces. Antiseptics are used to kill or eliminate microorganisms on living surfaces such as skin or mucous membranes. Sterilizing agents are used to eliminate or kill all microorganisms, including bacterial spores, on surfaces or objects.

It is important to note that the use of antimicrobial agents can lead to the emergence of antimicrobial-resistant microorganisms, which can cause serious and difficult to treat infections. Therefore, the proper use of these agents is critical to avoid the development and spread of antimicrobial resistance.