Antimicrobial agents

(microbiology) A chemical compound that either destroys or inhibits the growth of microscopic and submicroscopic organisms.

Chemical compounds biosynthetically or synthetically produced which either destroy or usefully suppress the growth or metabolism of a variety of microscopic or submicroscopic forms of life. On the basis of their primary activity, they are more specifically called antibacterial, antifungal, antiprotozoal, antiparasitic, or antiviral agents. Antibacterials which destroy are bactericides or germicides; those which merely suppress growth are bacteriostatic agents. See also Antibiotic; Fungistat and fungicide.

Of the thousands of antimicrobial agents, only a small number are safe chemotherapeutic agents, effective in controlling infectious diseases in plants, animals, and humans. A much larger number are used in almost every phase of human activity: in agriculture, food preservation, and water, skin, and air disinfection. A compilation of some common uses for antimicrobials is shown in the table.

The most important antimicrobial discovery of all time, that of the chemotherapeutic value of penicillin, was made in 1938. In the next 20 years, more than a score of new and useful microbially produced antimicrobials entered into daily use. New synthetic antimicrobials are found today by synthesis of a wide variety of compounds, followed by broad screening against many microorganisms. Biosynthetic antimicrobials, although first found in bacteria, fungi, and plants, are now being discovered primarily in actinomycetes.

Antimicrobial agents contain various functional groups. No particular structural type seems to favor antimicrobial activity. The search for correlation of structure with biological activity goes on, but no rules have yet appeared with which to forecast activity from contemplated structural changes. On the contrary, minor modifications may lead to unexpected loss of activity.