Case #17:

Clinical Presentation:
A 39 year-old-woman presents to the hospital with headache, blurry vision, fever and new right-sided hemiplegia. She has a history of inflammatory bowel disease and is maintained on steroids. A MRI of the brain showed a focal CNS lesion. Blood cultures are growing a gram-positive rod.

Clinical Diagnoses:
CNS Tumor

Microscopic examination:
Case 17 Image 1: Gram-stain of blood culture showing pleomorphic gram-positive bacilli.

Discussion:
Microbiologic Diagnosis:
Listeria Cerebritis
Culture of this organism on blood agar shows glistening colonies surrounded by a small zone of beta (clear) hemolysis (Case 17 Image 2). Transmitted by contaminated food sources, Listeria monocytogenes is a motile, non-spore-forming bacillus. Neonates, pregnant women and the immunocompromised patient are at increased risk for developing bacteremia and meningitis.

Maternal Listeriosis can be transmitted to the unborn transplacentally. This may result in stillbirth and abortion as a consequence of widespread infection and abscessing of many organs, including skin, spleen, liver (Case 17 Image 3). This is known as Granulomatosis infantiseptica.