Listeriosis laboratory tests

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Listeriosis Microchapters


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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]


For symptomatic patients, diagnosis of listeriosis is confirmed following the isolation of Listeria monocytogenes from a normally sterile site, such as blood, spinal fluid (in the setting of nervous system involvement), or amniotic fluid/placenta (in the setting of pregnancy). Cultures from non-sterile sites, such as stool samples, are not recommended (1-15% carriage rate) but may still be useful in gastroenteritis with high suspicion of listeriosis. Listeria monocytogenes may be isolated readily on routine media. Since Listeria is an intracellular organism, only 1/3 of cultures yield positive Gram-stains. Selective enrichment media improve rates of isolation from contaminated specimens. The cultures typically require 1-2 days for growth. A negative culture does not rule out infection in the presence of strong clinical suspicion. Cerebrospinal fluid (CSF) analysis may confirm the diagnosis among patients with CNS listeriosis. Serological tests (e.g. listeriolysin O titers) have been used, but their use remains controversial and are currently not recommended. Polymerase chain reaction for the detection of the HLY gene may be diagnostic, but it is not yet widely available for commercial use. Laboratory testing on asymptomatic patients (including high-risk asymptomatic patients) is not recommended.[1]

Laboratory Tests

The gold standard for the diagnosis of listeriosis is culture from sterile sites.


  • Diagnosis of listeriosis is made by culturing Listeria from sterile sites (e.g. blood, spinal fluid).
  • Cultures from non-sterile sites, such as stool culture or vaginal culture, are not helpful for the diagnosis of listeriosis (approximately 5% to 15% fecal carriage, especially among patients who receive PPI therapy).[2]
  • Gram-stain may yield positive results in approximately 1/3 of infected patients (Listeria is an intracellular organism).
  • Listeria grows on media such as Mueller-Hinton agar.
  • Identification is enhanced if the primary cultures are performed on agar containing sheep blood given the characteristic small zone of hemolysis that can be observed around, and under the colonies.
  • Isolation can be enhanced if the tissue is kept at 4°C for some days before inoculation into bacteriologic media.
  • The motility at room temperature and hemolysin production are primary findings that help differentiate Listeria from other organisms (e.g. coryneform bacteria).
  • The cultures typically require 1-2 days for growth.

Stool Cultures

  • Stool cultures are not indicated in systemic listeriosis patients because routine culture media for enteric pathogens are not appropriate for the growth of Listeria.
  • In cases of outbreaks of listeriosis or individual patients with suspected listerial gastroenteritis, special selected media can be used.

Listeriolysin O Titers

CSF Analysis

  • CSF analysis may confirm the diagnosis of listeriosis. Common findings include:

Polymerase Chain Reaction (PCR)


  1. "Listeria".
  2. Lennon D, Lewis B, Mantell C, Becroft D, Dove B, Farmer K; et al. (1984). "Epidemic perinatal listeriosis". Pediatr Infect Dis. 3 (1): 30–4. PMID 6701102.
  3. Salamina G, Dalle Donne E, Niccolini A, Poda G, Cesaroni D, Bucci M; et al. (1996). "A foodborne outbreak of gastroenteritis involving Listeria monocytogenes". Epidemiol Infect. 117 (3): 429–36. PMC 2271639. PMID 8972666.
  4. Dalton CB, Austin CC, Sobel J, Hayes PS, Bibb WF, Graves LM; et al. (1997). "An outbreak of gastroenteritis and fever due to Listeria monocytogenes in milk". N Engl J Med. 336 (2): 100–5. doi:10.1056/NEJM199701093360204. PMID 8988887.
  5. Mylonakis E, Hohmann EL, Calderwood SB (1998). "Central nervous system infection with Listeria monocytogenes. 33 years' experience at a general hospital and review of 776 episodes from the literature". Medicine (Baltimore). 77 (5): 313–36. PMID 9772921.
  6. 6.0 6.1 Southwick FS, Purich DL (1996). "Intracellular pathogenesis of listeriosis". N. Engl. J. Med. 334 (12): 770–6. doi:10.1056/NEJM199603213341206. PMID 8592552.
  7. Durand ML, Calderwood SB, Weber DJ, Miller SI, Southwick FS, Caviness VS, Swartz MN (1993). "Acute bacterial meningitis in adults. A review of 493 episodes". N. Engl. J. Med. 328 (1): 21–8. doi:10.1056/NEJM199301073280104. PMID 8416268.
  8. Hansen PB, Jensen TH, Lykkegaard S, Kristensen HS (1987). "Listeria monocytogenes meningitis in adults. Sixteen consecutive cases 1973-1982". Scand. J. Infect. Dis. 19 (1): 55–60. PMID 3105048.
  9. Uldry PA, Kuntzer T, Bogousslavsky J, Regli F, Miklossy J, Bille J, Francioli P, Janzer R (1993). "Early symptoms and outcome of Listeria monocytogenes rhombencephalitis: 14 adult cases". J. Neurol. 240 (4): 235–42. PMID 8496712.
  10. Lavetter A, Leedom JM, Mathies AW, Ivler D, Wehrle PF (1971). "Meningitis due to Listeria monocytogenes. A review of 25 cases". N Engl J Med. 285 (11): 598–603. doi:10.1056/NEJM197109092851103. PMID 4998254.

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