A 2-year-old child was admitted to the hospital with acute meningitis. The Gram stain revealed Gram-positive short rods, and the mother indicated that the child had received “all” of the meningitis vaccinations. What is the most likely cause of the disease?
**Core Concept**
The child's presentation with acute meningitis, Gram-positive short rods on Gram stain, and a history of full vaccination against meningitis suggests a case of meningitis caused by a non-vaccine serogroup of Neisseria meningitidis. However, the Gram stain morphology indicates a different pathogen. The most likely cause in this scenario is a bacterial pathogen that is commonly associated with meningitis in children, particularly those who have been vaccinated against other serogroups of Neisseria meningitidis.
**Why the Correct Answer is Right**
The Gram-positive short rods are likely Listeria monocytogenes, a common cause of meningitis in neonates and immunocompromised individuals, but can also affect healthy individuals, including children. Listeria monocytogenes can cause meningitis, particularly in children who have received vaccinations against other bacterial pathogens. The bacteria can enter the body through contaminated food or water, and the infection can spread to the central nervous system, leading to meningitis. The bacteria are Gram-positive and have a characteristic short rod shape.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is a type of bacteria that is typically associated with skin and soft tissue infections, not meningitis.
**Option B:** This option is incorrect because it is a type of bacteria that is typically associated with gastrointestinal infections, not meningitis.
**Option C:** This option is incorrect because it is a type of bacteria that is typically associated with respiratory infections, not meningitis.
**Clinical Pearl / High-Yield Fact**
Listeria monocytogenes is a Gram-positive bacterium that can cause meningitis in children, particularly those who have received vaccinations against other bacterial pathogens. It is essential to consider Listeria monocytogenes in the differential diagnosis of meningitis in children, especially in the context of a history of vaccination against other serogroups of Neisseria meningitidis.
**Correct Answer:** C. Listeria monocytogenes.