An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention of such infections. They may either kill or inhibit the growth of bacteria. A limited number of antibiotics also possess antiprotozoal activity.Antibiotics are not effective against viruses such as the common cold or influenza drugs which inhibit viruses are termed antiviral drugs or antivirals rather than antibiotics.
Carbon compounds obtained from some bacteria and fungi for destroying or preventing
the growth of harmful micro-organisms are called ‘antibiotics’. Antibiotics, a discovery of the 20th century, have brought about a revolution in the field of medicine. Even a disease like tuberculosis has been almost completely eradicated from some countries. Antibiotics mainly act against bacteria. Some antibiotics can destroy protozoa.
Some antibiotics are useful against a wide variety of bacteria. They are called broad-
spectrum antibiotics. Examples are ampicillin, amoxicillin, tetracycline, etc. When the pathogen cannot be identified even though the symptoms of disease are visible, broad spectrum antibiotics are used.
Whenever a pathogenic micro-organism is definitely known, then narrow-spectrum antibiotics are used. Examples are penicillin, gentamycin, erythromycin, etc.
