Question: Which foodborne pathogen accounts for approximately 20 percent of bacterial meningitis in individuals older than 60 years of age and has been associated with unpasteurized milk and soft cheese ingestion?
Answer: According to the cited reference, “Listeria monocytogenes, a gram-positive rod, is a foodborne pathogen with a tropism for the central nervous system. L. monocytogenes outbreaks have been associated with unpasteurized milk, soft cheeses, and deli-style meats. Illness, though rare in the general population, is an important cause of disease in newborns, pregnant women, the elderly, and people with impaired, cell-mediated immunity, such as transplant recipients and patients with AIDS. In 1995, the Centers for Disease Control and Prevention reported that L. monocytogenes accounted for 20% of bacterial meningitis cases among people >60 years of age. Presentation may be more subacute (>24 hours) than it is with other forms of bacterial meningitis. Cerebrospinal fluid Gram’s stain may be positive in only 30% to 40% of cases.
Pregnant women are also at increased risk for listeria infection. In this population, it causes chorioamnionitis in the woman (not meningitis), which at the time of delivery can lead to neonatal meningitis. Because of this risk, pregnant women are advised to avoid foods that may be sources of listeria infection, such as soft cheeses and deli meats”. (New England Journal of Medicine “Question of the Week” December 27, 2016)