Listeriosis other diagnostic studies
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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]
Overview
For symptomatic patients, diagnosis is confirmed only after 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). Importantly, a negative culture does not rule out infection in the presence of strong clinical suspicion. Serological tests are unreliable, and not recommended at the present time. Some additional serological and laboratory findings are associated with Listeriosis. MRI images may be used for the diagnosis of CNS infections
Other Laboratory Studies
CSF analysis
CSF analysis may lead to the confirmation of listeriosis. Common findings include:
- Pleocytosis
- More than 25 lymphocytes in CSF differential count, without antibiotic therapy
- Moderately elevated CSF protein concentration with reduced CSF glucose concentration[1]
- Despite the name "monocytogenes", more that half the patients have increased levels of neutrophils in CSF.
- Gram stain of the CSF has very low sensitivity and even when organisms are seen, they may be misidentified. [2] Therefore, Listeria monocytogenes should always be considered when similar organisms are growing in blood or CSF cultures. The presumptive diagnosis of viral meningitis should also be carefully considered in immunocompromised, chronically ill, or elderly patients, presenting with acute meningitis and a negative Gram stain. In rhombencephalitis patients diagnosis is often delayed because CSF examination reveals only mild abnormalities.
- A polymerase chain reaction assay has been developed for the hly gene detection, which encodes for the listeriolysin O, in CSF cultures. However, despite a high specificity and more sensitivity, it is not commercially available yet.
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. However, in cases of outbreaks of listeriosis or individual patients with suspected listerial gastroenteritis, special selected media can be used. The special culture media may be suggested by a local microbiology laboratory, a state health department or the CDC.
Serodiagnosis
Diagnosis of listeriosis with antibodies for listeriolysin O can be useful among infected patients with noninvasive disease.[3]
Imaging studies
Although both MRI and CT scan may be used to help in the diagnosis of Listeria monocytogenes lesions, MRI is a more sensitive method to detect listerial lesions in the cerebellum, brainstem and cortex.[4] On MRI, high-signal lesions on T2-weighted images and enhancing lesions on T1-weighted images can be identified in the cerebral parenchyma on MRI following administration of IV contrast. Since brainstem involvement on MRI coupled with proper clinical setting is strongly suggestive of infection by Lysteria, it is recommended the use of contrast MRI in all patients presenting with listerial meningitis, listerial bacteremia, CNS signs and symptoms or suspicion of intracranial listeriosis.
Anton Test
- Used in the identification of Listeria monocytogenes
- Instillation of a culture into the conjunctival sac of a rabbit or guinea pig causes severe keratoconjunctivitis within 24 hours.[5][6]
References
- ↑ 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.
- ↑ 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.
- ↑ Mandell, Gerald L.; Bennett, John E. (John Eugene); Dolin, Raphael. (2010). Mandell, Douglas, and Bennett's principles and practice of infectious disease. Philadelphia, PA: Churchill Livingstone/Elsevier. ISBN 0-443-06839-9.
- ↑ Armstrong RW, Fung PC (1993). "Brainstem encephalitis (rhombencephalitis) due to Listeria monocytogenes: case report and review". Clin Infect Dis. 16 (5): 689–702. PMID 8507761.
- ↑ "Anton test - definition of Anton test in the Medical dictionary - by the Free Online Medical Dictionary, Thesaurus and Encyclopedia". Medical-dictionary.thefreedictionary.com. Retrieved 2013-08-05.
- ↑ "Anton's eye test". Whonamedit. Retrieved 2013-08-05.