Antibiotics - Practice Questions & MCQ

The term antibiotics have been derived from the word 'Antibiosis' which means survival of fittest, i.e., a process in which one organism may destroy another to preserve itself. It is a chemical substance produced by or derived from living cells which is capable of inhibiting the life processes or even destroying microorganisms.

The first antibiotic, discovered by Alexander Fleming in 1929 from the mould Penicillium notatum, was penicillin. In 1938, Ernst Chain and Howard Florey isolated penicillin in pure form and proved its effectiveness as an antibiotic. It was against the large number of infections caused by various cocci, gram positive bacteria, etc. It is an effective drug for pneumonia, bronchitis, sore throat and abscesses.

In penicillin, a four-membered ring is fused to another five-membered ring. Structures of individual penicillins are given in the table. Penicillin-G is the most commonly used. The penicillins are only sparingly soluble in water. However, their sodium or potassium salts are soluble in water. Pennicilins are found to be actve against gram-positive stains. However, these are ineffective against gram-negative organisms. Organisms sometimes develop resistance to penicillins. Penicillins generally have low toxicity in comparison to sulpha drugs. However, in some cases, allergic reactions may result in. Penicillin is thus, given after a test prick.

The antibiotics can either be bactericidal or bacteriostatic. Examples are:

• Bactericidal: The drugs which kill the organism in the body. For example, penicillin, ofloxacin, and aminoglycosides.
• Bacteriostatic: The drugs which inhibit or check the growth of the organism in the body. For example, tetracycline, chloramphenicol and erythromycin.