Which of the following drugs is a bacteriostatic agent?

DSSSB 6 September 2024

Pharmacology

Easy

Appeared in: DSSSB 6 September 2024

Explanation

Ethambutol is classified as a bacteriostatic agent, which means it primarily inhibits the growth and multiplication of Mycobacterium tuberculosis rather than killing the bacteria outright.
Its mechanism of action involves inhibiting arabinosyl transferase, an enzyme necessary for the synthesis of arabinogalactan, a key component of the mycobacterial cell wall.
By halting bacterial reproduction, Ethambutol allows the host's immune system to control and eliminate the infection.
Among the first-line anti-TB drugs, it is unique in its bacteriostatic nature, while others like Isoniazid and Rifampicin are bactericidal.

Option A: Rifampicin is a potent bactericidal drug. It kills bacteria by inhibiting their DNA-dependent RNA polymerase, which prevents the synthesis of RNA and essential proteins.
Option B: Streptomycin is a bactericidal antibiotic from the aminoglycoside class. It works by binding to the 30S ribosomal subunit of the bacteria, causing misreading of the genetic code and inhibiting protein synthesis, which leads to cell death.
Option C: Isoniazid is a primary bactericidal agent, especially against actively dividing mycobacteria. It inhibits the synthesis of mycolic acids, which are essential components of the mycobacterial cell wall.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Classification of Anti-Tuberculosis Drugs (Bacteriostatic vs. Bactericidal) as background academic context rather than a clinical decision trigger.
Understanding the distinction between bacteriostatic and bactericidal drugs is vital for creating effective combination therapies for tuberculosis, which aim to rapidly kill bacteria and prevent the emergence of drug resistance.
A key nursing responsibility when a patient is on Ethambutol is to monitor for optic neuritis. This involves performing baseline and regular visual acuity and red-green color discrimination tests.
Patient education is critical. The nurse must instruct the patient to report any visual changes immediately, as this side effect can be irreversible if not caught early.

How to Approach the Question

First, identify the key term in the question: 'bacteriostatic agent'.
Recall the definitions of bacteriostatic (inhibits bacterial growth) and bactericidal (kills bacteria).
Mentally review the standard first-line anti-tuberculosis drugs: Isoniazid (INH), Rifampicin (RIF), Pyrazinamide (PZA), and Ethambutol (EMB).
Categorize each drug based on its primary action. Remember that INH, RIF, and PZA are the core bactericidal agents.
Identify Ethambutol as the primary bacteriostatic agent in this group.
Select the option corresponding to Ethambutol.

Concept Tested & Keywords

Concept Tested: Classification of Anti-Tuberculosis Drugs (Bacteriostatic vs. Bactericidal)
Stem keywords: bacteriostatic agent, drug
Lead-in keywords: Which

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