DOC for listeria meningitis –
**Core Concept**
Listeria meningitis is a severe infection caused by the bacterium *Listeria monocytogenes*, which can lead to meningitis and other life-threatening complications. The disease primarily affects immunocompromised individuals, pregnant women, and the elderly.
**Why the Correct Answer is Right**
The drug of choice (DOC) for listeria meningitis is ampicillin, which is a broad-spectrum penicillin antibiotic. Ampicillin works by inhibiting the synthesis of the bacterial cell wall, ultimately leading to the death of the bacteria. This is particularly effective against *Listeria monocytogenes*, as it is susceptible to ampicillin. The combination of ampicillin and an aminoglycoside, such as gentamicin, is often used to enhance bactericidal activity and prevent the emergence of resistance.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because other antibiotics like ceftriaxone may not be effective against *Listeria monocytogenes*, and their use may delay the initiation of appropriate therapy.
* **Option B:** This option is incorrect because vancomycin is primarily used to treat infections caused by gram-positive bacteria, and its effectiveness against *Listeria monocytogenes* is not well established.
* **Option C:** This option is incorrect because trimethoprim-sulfamethoxazole is not the preferred treatment for listeria meningitis, and its use may be associated with resistance.
**Clinical Pearl / High-Yield Fact**
It is essential to consider listeria meningitis in the differential diagnosis of meningitis in immunocompromised patients, particularly those with a history of exposure to contaminated foods.
**Correct Answer:** A. Ampicillin