Acid fast staining used in the above slide showing mycobacterium tuberculi is named:

AIIMS Jodhpur SNO-2023

Applied Microbiology & Infection control

Easy

Appeared in: AIIMS Jodhpur SNO-2023

Explanation

The Ziehl-Neelsen (ZN) stain is the classic method used to identify acid-fast bacilli like Mycobacterium tuberculosis.
The high mycolic acid (waxy lipid) content in the cell wall of M. tuberculosis makes it resistant to decolorization by acid after staining.
In the ZN method, the bacteria retain the primary red stain (carbol fuchsin) and appear as red or pink rods against a blue background (counterstained with methylene blue), exactly as shown in the image.
This staining method is a cornerstone in the diagnosis of tuberculosis from clinical samples like sputum.

Option A: Gram staining differentiates bacteria into Gram-positive (purple) and Gram-negative (pink) based on the peptidoglycan content of their cell walls. It is ineffective for M. tuberculosis because the waxy mycolic acid layer prevents the Gram stains from penetrating the cell wall properly.
Option B: Albert's staining is a special method used to stain the metachromatic (volutin) granules of Corynebacterium diphtheriae, the bacterium that causes diphtheria. It stains the bacilli green and the granules bluish-black.
Option C: Giemsa staining is primarily used in hematology and for identifying blood parasites like Plasmodium (malaria) and certain intracellular organisms like Chlamydia and Rickettsia. It is not the standard stain for M. tuberculosis.

Visual 1: Flowchart - A step-by-step flowchart illustrating the Ziehl-Neelsen staining procedure (Application of Carbol Fuchsin with heat -> Decolorization with Acid-Alcohol -> Counterstaining with Methylene Blue).
Visual 2: Comparative Diagram - A side-by-side comparison of microscopic images showing the results of Ziehl-Neelsen, Gram, and Albert's stains on their respective target bacteria.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Identification of microbiological staining techniques, specifically for Mycobacterium tuberculosis as background academic context rather than a clinical decision trigger.
Sputum smear microscopy using ZN staining is a rapid and crucial first-line diagnostic tool for pulmonary tuberculosis, especially in resource-limited settings.
Nurses are responsible for collecting high-quality sputum samples (early morning, deep cough) and ensuring they are transported to the lab promptly and safely.
A positive AFB smear result requires immediate implementation of airborne infection isolation precautions to prevent transmission of TB to healthcare workers and other patients.

How to Approach the Question

First, carefully analyze the provided image. Note the distinct colors and shapes of the microorganisms and the background. You can see bright red, rod-shaped organisms against a blue background.
Next, read the question stem, which specifically mentions 'Acid fast staining' and 'mycobacterium tuberculi'.
Connect the visual information with the keywords from the question. The appearance in the image is the classic result of an acid-fast stain on M. tuberculosis.
Recall the different types of microbiological stains and their specific applications.
Evaluate the given options. 'Gram staining', 'Albert's staining', and 'Giemsa staining' are used for different purposes and yield different results.
Select 'Ziehl-Neelsen staining' as it is the specific name for the acid-fast staining method used to identify Mycobacterium species.

Concept Tested & Keywords

Concept Tested: Identification of microbiological staining techniques, specifically for Mycobacterium tuberculosis.
Stem keywords: Acid fast staining, slide, mycobacterium tuberculi
Lead-in keywords: is named
Clinical cues: The image shows red, rod-shaped bacteria on a blue background, which is the classic result of acid-fast staining.

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