Minimum number of mycobacteria required to be detected by AFB staining is (per ml):
**Core Concept**
Mycobacterial acid-fast bacilli (AFB) staining is a crucial diagnostic tool for detecting mycobacterial infections, such as tuberculosis (TB). The technique relies on the resistance of mycobacterial cell walls to decolorization with acid alcohol, allowing them to be stained and visualized under a microscope.
**Why the Correct Answer is Right**
The minimum number of mycobacteria required to be detected by AFB staining is 10,000 organisms per milliliter (ml) of sputum. This is because the sensitivity of the technique is limited by the number of organisms that can be stained and visualized. The Ziehl-Neelsen stain, a commonly used AFB staining method, requires a large number of organisms to be present in the sample for detection. The presence of a large number of organisms increases the likelihood of detecting AFB-positive cells under the microscope.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is lower than the actual minimum number of mycobacteria required for detection.
**Option B:** This option is incorrect because it is higher than the actual minimum number of mycobacteria required for detection.
**Option C:** This option is incorrect because it is not a valid number, making it an implausible answer choice.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that AFB staining is a qualitative test, and a negative result does not rule out mycobacterial infection. A combination of clinical evaluation, radiographic findings, and other diagnostic tests is often required to confirm the diagnosis of TB or other mycobacterial infections.
**Correct Answer: 10,000**