LisiteriaMonocytogenes is typically transmitted from ingestion of contaminated food such as unpasteurized milk or cheese, raw foods, and recently cantaloupes; transmission from veterinary exposure, infected soil and water have also been reported.
Listeria has a predilection for the central nervous system (CNS) causing several infections including meningioencephalitits, brain or spinal abscess, cerebritis (infection of brain parenchyma), and rhomboencephalitis (encephalitis of the brainstem).
Risk factors include immunosuppression, advanced age, newborns, and pregnancy.
There is no clinical way to distinguish CNS infection with Listeria from other pathogens, therefore blood and cerebrospinal fluid (CSF) culture is required.
CSF analysis demonstrates pleocytosis, elevated protein, and low glucose. CSF gram stain has a low sensitivity (~33%), but consider Listeria in the differential if "diptheroid-like" bacteria are reported on gram stain.
Ampicillin is the drug of choice and should be continued for at least three weeks (sometimes longer). Adding gentamycin is sometimes recommended for synergy in severe infection.
References
Mylonakis E, Hohmann EL, Calderwood SB. Central nervous system infection with Listeriamonocytogenes. 33 years' experience at a general hospital and review of 776 episodes from the literature. Medicine (Baltimore). Sep 1998;77(5):313-36.
