For which of the following diseases is the Acid Fast Bacilli Test positive?

MP CHO-2020

Applied Microbiology & Infection control

Easy

Appeared in: MP CHO-2020

Explanation

Tuberculosis and Leprosy are caused by bacteria from the Mycobacterium genus (M. tuberculosis and M. leprae, respectively).
The cell walls of Mycobacteria contain a high concentration of mycolic acid, a waxy substance that makes them impermeable to many stains.
This mycolic acid property makes the bacteria 'acid-fast,' meaning they resist decolorization by acid-alcohol after being stained with a primary dye like carbol fuchsin.
The Ziehl-Neelsen (ZN) stain is the classic method for AFB testing, where acid-fast bacilli appear as red or pink rods against a blue counterstain background, confirming a positive test for both diseases.

Option A: This option is incorrect because Tetanus is not diagnosed using an Acid-Fast Bacilli test.
Option B: This option is incorrect because neither Diphtheria nor Tetanus are caused by acid-fast bacilli.
Option C: This option is incorrect because Poliomyelitis is a viral disease, and Tetanus is caused by a non-acid-fast bacterium.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Microbiological diagnosis using Acid-Fast Bacilli (AFB) staining as background academic context rather than a clinical decision trigger.
AFB smear microscopy is a rapid, inexpensive, and crucial first-line diagnostic tool for identifying infectious cases of pulmonary TB, guiding immediate patient isolation and treatment initiation.
In leprosy, identifying AFB in slit-skin smears helps confirm the diagnosis and classify the disease into paucibacillary or multibacillary types, which determines the duration and regimen of multi-drug therapy.
Nurses are responsible for collecting appropriate specimens (e.g., sputum for TB, assisting with slit-skin smears for leprosy) and ensuring they are handled safely to prevent transmission.

How to Approach the Question

First, identify the key term in the question: 'Acid Fast Bacilli Test'.
Recall the principle of this test: it is a specific stain designed to identify bacteria with waxy, mycolic acid-rich cell walls.
Remember the primary genus of bacteria that are acid-fast: Mycobacterium.
Link the Mycobacterium genus to the major diseases it causes, which are Tuberculosis (M. tuberculosis) and Leprosy (M. leprae).
Evaluate the given options. The only option that includes both of these diseases is 'Tuberculosis and Leprosy'.
Systematically eliminate the other options by recalling the causative agents of the other diseases: Tetanus is caused by Clostridium (non-AFB), Diphtheria by Corynebacterium (non-AFB), and Poliomyelitis is a viral disease.

Concept Tested & Keywords

Concept Tested: Microbiological diagnosis using Acid-Fast Bacilli (AFB) staining.
Stem keywords: Acid Fast Bacilli Test, positive
Lead-in keywords: For which
Negative lead-in flag: false

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