Microbiology

Chemotherapeutic Agents And Chemotherapy

Chemotherapeutic agents are chemical substances used for the treatment of infectious diseases or disease by the proliferation of malignant cells. These substances are prepared in the chemical laboratory or obtained from microorganisms and some plants and animals. In general, naturally occurring substances are distinguished form synthetic one by the term “antibiotics”. However, some antibiotics are prepared in laboratory while other are obtained from microbial biosynthesis.

Antitoxins and other substances produced by the bodies of infected animals are not considered as chemotherapeutic agents. Compounds used for killing or inhabiting microorganisms growth in vitro are not classified as chemotherapeutic agents but usually as disinfectant, antiseptics, or germicides.

To be useful as a chemotherapeutic agent a substance must have selectively toxicity for the parasite, which means a low toxicity for host cells and high toxicity for the parasite.

A Satisfactory Chemotherapeutic Agent Must Have

1 Destroy or prevent the activity of a parasite without injuring the cells of the host or with only minor injury to its cells.

2 Be able to come in contact with the parasite by penetrating the cells and tissues of the host in effective concentration.

3 Leave unaltered the host’s natural defence mechanisms, such as phagocytosis and the production of antibodies.

Characteristics Of Antibiotics That Qualify Them As Chemotherapeutic Agents

To be useful as chemotherapeutic agents antibiotics must have the following qualities.

1 they should have the ability to destroy or inhibit many different species of pathogenic microorganisms. This is what is meant by a “broad-spectrum” antibiotic.

2 they should prevent the ready development of resistant forms of the parasite.

3 they should not produce undesirable side effects in the host, such as sensitivity or allergic reactions, nerve damage, or irritation of the kidneys and gastrointestinal tract.

4 they should not eliminate the normal microbial flora of the host, because doing so may upset the “balance of nature” and permit normally non-pathogenic microbes, or particularly pathogenic forms normally resistant by the usual flora, to establish a new infection.

Antibiotics And Their Mode Of Action

Antibiotics can be classified in several ways, for example, some are bactericidal while others are bacteriostatic. They may be grouped on the bases of chemical structure. A third way of classification of antibiotics is on the bases of their mode of action. Here we would discuss antibiotics acting on the bases of their mode of action.

The Major Points Of Attack Of Antibiotics On Microorganisms Include

Inhibition of cell wall synthesis

Damage to the cytoplasmic membrane

Inhibition of nucleic acid and protein synthesis

Inhibition of specific enzyme system


Reference: Microbiology Pelczar

Gaurav Singh

Editor in Chief Medical Microbiology & Recombinant DNA Technology (RDT) Labs - RDT Labs Magazine

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