**Core Concept**
Neonatal meningitis is a serious infection that occurs in newborns, often caused by pathogens acquired from the maternal genital tract during delivery. The most common causative agents include group B streptococcus, Escherichia coli, and Listeria monocytogenes.

**Why the Correct Answer is Right**
Listeria monocytogenes is a gram-positive bacterium that can be transmitted to the fetus or neonate through the maternal genital tract. This occurs when the mother's immune system is compromised, allowing the bacterium to colonize the genital tract. Listeria monocytogenes can then be transmitted to the neonate during delivery, potentially leading to severe infections such as meningitis or sepsis.

**Why Each Wrong Option is Incorrect**
**Option A:** Group B streptococcus is a common cause of neonatal sepsis and meningitis, but it is typically acquired from the maternal genital tract during delivery, not through the maternal genital tract before birth.
**Option B:** Escherichia coli is another common cause of neonatal sepsis and meningitis, but it is typically acquired from the maternal genital tract during delivery or from the environment.
**Option C:** This option is not a known causative agent of neonatal meningitis.

**Clinical Pearl / High-Yield Fact**
Neonatal meningitis is a medical emergency that requires prompt recognition and treatment. The most important risk factor for neonatal meningitis is premature birth, and the most common presentation is a febrile neonate with seizures or altered mental status.

**Correct Answer:** C. Listeria monocytogenes.