Listeriosis other diagnostic studies
Listeriosis Microchapters |
Diagnosis |
---|
Treatment |
Case Studies |
Listeriosis other diagnostic studies On the Web |
American Roentgen Ray Society Images of Listeriosis other diagnostic studies |
Risk calculators and risk factors for Listeriosis other diagnostic studies |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
The diagnosis should be established based on the clinical findings, complemented by culture of the organism from blood and CSF. In many reported cases, despite the presence of the disease, CSF cultures were negative, in which cases, blood cultures should orient the diagnosis, since these are more commonly positive than the first ones.[1]
Other Laboratory Studies
The methods for analysis of food are complex and time-consuming. The present Food and Drug Administration (FDA) method, revised in September, 1990, requires 24 and 48 hours of enrichment, followed by a variety of other tests. Total time for identification takes from 5 to 7 days, but the announcement of specific nonradiolabled DNA probes should soon allow a simpler and faster confirmation of suspect isolates.
Recombinant DNA technology may even permit 2-to-3 day positive analysis in the future. Currently, the FDA is collaborating in adapting its methodology to quantitate very low numbers of the organisms in foods.
CSF analysis
- Pleocytosis
- More than 25 lymphocytes in CSF differential count, without antibiotic therapy.
- Moderately elevated CSF protein concentration with reduced CSF glucose concentration.[2]
- Gram stain of the CSF has very low sensitivity and even when organisms are seen, they may be misidentified. [3] 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. Due to the fact that rhombencephalitis patients CSF examination often reveals only mild abnormalities, its diagnosis is often delayed.
- A Polymerase chain reaction assay has been developed for the hly gene detection, which encodes for the listeriolysin O, in CSF cultures. However, despite more specific and more sensitive, it is not commercially available yet.
- Stool cultures for Listeria are not indicated in systemic listeriosis patients, since 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 have proven useful for diagnosis of infected patients with noninvasive disease[4].
Imaging studies
Although both MRI and CT scan may be used to help in the diagnosis of Listeria monocytogenes lesions, the MRI is a more sensitive method to detect listerial lesions in the cerebellum, brainstem and cortex.[1] On an MRI, in the cerebral parenchyma there may be identified high-signal lesions on T2-weighted images and enhancing lesions on T1-weighted images, following administration of IV contrast. Since MRI evidence of brainstem involvement, 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
- A 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]
Cell Culture
- Listeria grows on media such as Mueller-Hinton agar.[7]
- Identification is enhanced if the primary cultures are done on agar containing sheep blood, because the characteristic small zone of hemolysis can be observed around and under 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 coryneform bacteria.
References
- ↑ 1.0 1.1 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.
- ↑ 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.
- ↑ "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.
- ↑ Chapter 13. Non-Spore-Forming Gram-Positive Bacilli: Corynebacterium, Propionibacterium, Listeria, Erysipelothrix, Actinomycetes, & Related Pathogens ,Jawetz, Melnick, & Adelberg's Medical Microbiology, 24th Edition ,The McGraw-Hill Companies