Chloroamphenicol is a _________.
(a) Narrow spectrum antibiotic
(b) Broad spectrum antibiotic
(c) Limited spectrum antibiotic
(d) Antiseptic drug

Question

UnlockIAS · Accepted Answer

Correct — option (2), 'Only (b) is correct'. The drug, printed here as 'Chloroamphenicol' and standardly spelt chloramphenicol, is the textbook example of a broad spectrum antibiotic. Antibiotics are graded by how wide a range of organisms they act against. A broad spectrum antibiotic kills or inhibits a wide range of both Gram-positive and Gram-negative bacteria; a narrow spectrum antibiotic is effective mainly against one of those two groups; a limited spectrum antibiotic is effective against a single organism or a single disease. Chloramphenicol, first isolated in 1947, sits squarely in the first class. It is rapidly absorbed from the gastro-intestinal tract, so it can be given by mouth, and it has been used against typhoid, dysentery, acute fever, certain urinary infections, meningitis and pneumonia — a list of unrelated conditions caused by unrelated organisms, which is itself the evidence of a broad spectrum. There is a structural shortcut worth seeing here too. The four statements are mutually exclusive descriptions of one substance: a drug cannot be both narrow spectrum and broad spectrum, nor both broad and limited, nor an antibiotic and an antiseptic. Any option asserting two of them at once is therefore self-defeating before the pharmacology is even considered, which disposes of options (1) and (3) in a single stroke and leaves the paper asking one plain question — antibiotic or antiseptic.

Why the other options are wrong — (a) This option fails twice over. First, it is internally impossible: it claims the same drug is a narrow spectrum antibiotic and an antiseptic drug, two categories that cannot both hold of one substance. Second, both of its limbs are wrong on the facts. Chloramphenicol is broad spectrum, not narrow — penicillin G is the standard example of a narrow spectrum antibiotic, effective mainly against Gram-positive organisms. And it is not an antiseptic: antiseptics are applied to living surfaces such as wounds, cuts and diseased skin, whereas chloramphenicol is a systemic antibiotic absorbed from the gut and carried in the blood.  (c) The trap here is that limb (b) is right, so a candidate who checks only the first thing he recognises will stop and mark it. But limb (c) contradicts limb (b). 'Limited spectrum' is a real category in the classification — it describes an antibiotic effective against a single organism or a single disease — and precisely because it is real, it is the opposite end of the same scale from 'broad spectrum'. A drug active against typhoid, dysentery, meningitis, pneumonia and urinary infections is by definition not limited to one organism. The lesson is that a partly-correct option is worth nothing; every limb of a compound option must survive.  (d) This makes chloramphenicol an antiseptic, which confuses two different classes of antimicrobial. Antiseptics are applied to living tissue and are chosen for not damaging it — dettol, which is a mixture of chloroxylenol and terpineol; tincture of iodine; iodoform; boric acid in dilute solution as an eye wash. Disinfectants act on inanimate surfaces such as floors, drains and instruments, and the same chemical can serve as either depending on concentration: a 0.2 per cent solution of phenol is an antiseptic while a 1 per cent solution is a disinfectant. Antibiotics are a separate class again — substances produced by micro-organisms, or made in part by synthesis, which act inside the body at low concentration to stop other micro-organisms growing.

Concept: Medicines that act against micro-organisms are sorted by where they are used and how widely they act. Antibiotics work within the body: they are substances produced wholly or partly by micro-organisms which, in low concentration, inhibit the growth of or destroy other micro-organisms by interfering with their metabolic processes. Antiseptics and disinfectants work on surfaces: antiseptics on living tissue, disinfectants on inanimate objects. Within antibiotics, the spectrum classification is the one examiners test. Broad spectrum drugs hit a wide range of Gram-positive and Gram-negative bacteria and include chloramphenicol, tetracycline, ampicillin, amoxycillin, ofloxacin and vancomycin. Narrow spectrum drugs act mainly on one of the two groups, penicillin G being the classical case. Limited spectrum drugs are effective against a single organism or disease. A second, independent classification splits antibiotics into bactericidal, which kill the organism, and bacteriostatic, which merely stop it multiplying and leave the killing to the body's own defences.

State PCS 2026 Q67 — Science & Technology PYQ with Answer

State PCS 2026 Q67 — Science & Technology PYQ with Answer