Which among the following is not a broad-spectrum antibiotics?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Penicillin
Antibiotics that kill or inhibit a wide range of Gram-positive and Gram-negative bacteria are broad spectrum antibiotics; those effective mainly against one group are narrow spectrum.
Option (1) Ofloxacin — A broad-spectrum antibiotic.
Option (2) Vancomycin — A broad-spectrum antibiotic.
Option (3) Penicillin — Not a broad-spectrum antibiotic. Penicillin G acts mainly on Gram-positive bacteria, so it has a narrow spectrum; only its synthetic modifications, ampicillin and amoxycillin, are broad spectrum.
Option (4) Chloramphenicol — A broad-spectrum antibiotic. It is given orally for typhoid, dysentery, meningitis and pneumonia.
Note 1: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Antibiotics – …
Note 2: The same/similar question has been asked in different years by NTA as per the details given below:
| 2026 | 2025 | 2024 | 2023 | 2022 |
|---|---|---|---|---|
| – | – | – | 02-06 S3 31-05 S1 | – |