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Monday 13 February 2006

Definition: Infection by Listeria monocytogenes.

In acute human infections, Listeria monocytogenes evokes an exudative pattern of inflammation with numerous neutrophils.

The meningitis it causes is macroscopically and microscopically indistinguishable from that caused by other pyogenic bacteria.

The finding of Gram-positive, mostly intracellular, bacilli in the CSF is virtually diagnostic. More varied lesions may be encountered in neonates and immunosuppressed adults.

Focal abscesses alternate with grayish or yellow nodules representing necrotic amorphous basophilic tissue debris.

These can occur in any organ, including the lung, liver, spleen, and lymph nodes. In infections of longer duration, macrophages appear in large numbers, eventually to dispose of the necrotic remnants, but true epithelioid cell granulomas are rare.

Infants born live with Listeria monocytogenes sepsis often have a papular red rash over the extremities, and listerial abscesses can be seen in the placenta. A smear of the meconium will disclose the Gram-positive organisms.


- systemic microabscesses
- systemic granuloma-like lesions containing histiocytes, monocytes, lymphocytes, and polymorphonuclear leukocytes with variable necrosis

- +/- organomegaly


- Klatt EC, Pavlova Z, Teberg AJ, Yonekura ML. Epidemic perinatal listeriosis at autopsy. Hum Pathol. 1986 Dec;17(12):1278-81. PMID: 3793087