A narrow-spectrum antibiotic is active against-

1. Gram-positive or gram-negative bacteria.
2.  Gram-negative bacteria only.
3. Single organism or one disease.
4. Both gram-positive and gram-negative bacteria.


Hint: Narrow-spectrum antibiotic is an antibiotic that is only able to kill or inhibit limited species of bacteria.

Antibiotics are now defined as chemical substances that in low concentration, either kill or inhibit the growth of microorganisms by intervening in their metabolic processes. The full range of microorganisms attacked by an antibiotic is called its spectrum.

Broad-spectrum antibiotics are effective against several different types of harmful bacteria i.e., a wide range of gram-positive and gram-negative bacteria.

These effective mainly against gram-positive or gram-negative bacteria are narrow-spectrum antibiotics.

Chloramphenicol is a broad-spectrum antibiotic and penicillin-G that has a narrow spectrum. If an antibiotic is effective against a single organism or disease then it is a limited spectrum antibiotic.