Listeria Monocytogenes Infection (Listeriosis) Workup

Updated: May 21, 2019
  • Author: Karen B Weinstein, MD, FACP; Chief Editor: Michael Stuart Bronze, MD  more...
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Workup

Laboratory Studies

Blood cultures should be performed. Blood culture results are positive in 60-75% of patients with CNS infections.

Listeria demonstrates "tumbling motility" in wet mounts of cerebrospinal fluid (CSF). Listeria organisms are motile in wet mounts of CSF.

CSF Gram stain results are positive in less than 50% of patients. CSF analysis reveals pleocytosis, and CSF protein levels are moderately elevated. CSF glucose levels may be low, and if so, are associated with a poor prognosis.

Laboratory results that show diphtheroids should prompt heightened awareness for the possibility of Listeria infection, particularly in immunocompromised patients.

CSF cultures are positive less frequently than blood cultures.

A commercially available PCR test has been developed for CSF analysis.

Serologic testing is not reliable.

Synovial fluid and/or prosthetic joint material should be cultured in cases of septic arthritis.

Stool cultures are neither sensitive nor specific.

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Imaging Studies

MRI is superior to CT scan for demonstrating CNS disease, especially in the brainstem. [12]

Transesophageal echocardiography should be performed if endocarditis is suspected.

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Procedures

Lumbar puncture should be performed if CSF infection is suspected.

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