Antimicrobial Agents Therapy and Resistance
Any chemical used in treatment, relief, or prophylaxis of disease is defined as a chemotherapeutic drug or agent. When chemothera-peutic drugs are given as a means to control infection, the practice is termed antimicrobial chemotherapy. Antimicrobial drugs (also termed anti-infective drugs) are a special class of compounds capable even in high dilutions of destroying or inhibiting micro-organisms. The origin of modern antimicrobial drugs is varied.
The antibiotics are substances produced by the natural meta-bolic processes of some microorganisms that can inhibit or destroy other microorganisms. Synthetic antimicrobial drugs are derived in laboratory from dyes or other organic compounds through chemical reactions. Although division into these two categories has been traditional, they tend to overlap, because most antibiotics, termedsemisynthetic antibiotics, are now chemi-cally altered in laboratory. The current trend is to use the term antimicrobic for all antimicrobial drugs, regardless of originAntimicrobial drugs vary in their spectrum of activities. They may be broad-spectrum or narrow-spectrum antibiotics.
Broad-spectrum or extended-spectrum antibiotics are activeagainst a wider range of different microbes. For example, tetra-cyclines are active against a variety of Gram-positive and Gram-negative bacteria, rickettsiae, mycoplasmas, and even protozoa.
Narrow-spectrum antibiotics are effective against one orvery few microbes. For example, vancomycin is active against certain Gram-positive bacteria (such as staphylococci and enterococci) or griseofulvin, which is used only against fungal skin infections.