Tober Ayer’s test is positive in which of the following condition?
**Core Concept**
Tober Ayer's test is a diagnostic tool used to detect the presence of anthrax, a bacterial infection caused by *Bacillus anthracis*. The test relies on the characteristic gelatinous edema that develops in the skin after exposure to anthrax spores.
**Why the Correct Answer is Right**
Tober Ayer's test is positive when a characteristic lesion, known as an eschar, develops at the site of exposure. This eschar is a result of the body's immune response to the anthrax toxin, which causes necrosis and tissue death. The toxin's mechanism of action involves the formation of a pore in the cell membrane, leading to cell lysis and the characteristic gelatinous edema.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Tober Ayer's test is not used to diagnose other bacterial infections, such as *Clostridium perfringens* or *Staphylococcus aureus*, which may cause similar skin lesions but have distinct underlying pathophysiology.
**Option B:** This option is incorrect because the test is not used to diagnose fungal infections, such as *Histoplasma capsulatum*, which may cause skin lesions but are not associated with the characteristic gelatinous edema seen in anthrax.
**Option C:** This option is incorrect because the test is not used to diagnose viral infections, such as herpes simplex, which may cause skin lesions but are not associated with the characteristic eschar seen in anthrax.
**Clinical Pearl / High-Yield Fact**
Tober Ayer's test is a classic example of a clinical correlation between a specific diagnostic test and a characteristic pathological finding. It is essential to remember that the test is positive when a characteristic eschar develops at the site of exposure, and not just in the presence of any skin lesion.
**Correct Answer: C. Cutaneous anthrax**