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| ==Overview== | | ==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
| | Additional studies for the diagnosis of listeriosis are not recommended. |
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| ==Other Laboratory Studies== | | ==Other Laboratory Studies== |
| ===CSF analysis===
| | Additional studies for the diagnosis of listeriosis are not recommended. |
| [[CSF]] analysis may lead to the confirmation of [[listeriosis]]. Common findings include:
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| * [[Pleocytosis]]
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| * More than 25 [[lymphocytes]] in [[CSF]] [[Differential blood count (patient information)|differential count]], without [[antibiotic]] therapy.
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| * Moderately elevated [[CSF]] [[protein]] concentration with reduced [[CSF]] [[glucose]] concentration.<ref name="pmid9772921">{{cite journal| author=Mylonakis E, Hohmann EL, Calderwood SB| title=Central nervous system infection with Listeria monocytogenes. 33 years' experience at a general hospital and review of 776 episodes from the literature. | journal=Medicine (Baltimore) | year= 1998 | volume= 77 | issue= 5 | pages= 313-36 | pmid=9772921 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=9772921 }} </ref>
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| * Despite the name "monocytogenes", more that half the patients have increased levels of [[neutrophils]] in [[CSF]].
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| * [[Gram stain]] of the [[CSF]] has very low [[sensitivity]] and even when organisms are seen, they may be misidentified. <ref name="pmid4998254">{{cite journal| author=Lavetter A, Leedom JM, Mathies AW, Ivler D, Wehrle PF| title=Meningitis due to Listeria monocytogenes. A review of 25 cases. | journal=N Engl J Med | year= 1971 | volume= 285 | issue= 11 | pages= 598-603 | pmid=4998254 | doi=10.1056/NEJM197109092851103 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=4998254 }} </ref> Therefore, ''Listeria monocytogenes'' should always be considered when similar organisms are growing in [[blood culture |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.
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| * 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 [[Specificity|specific]] and more [[sensitivity|sensitive]], it is not commercially available yet.
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| ===Stool cultures===
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| 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]].
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| ===Serodiagnosis===
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| [[Diagnosis]] of [[listeriosis]] with [[antibodies]] for ''[[listeriolysin O]]'' have proven useful for [[diagnosis]] of [[infected]] patients with noninvasive disease.<ref>{{Cite book | last1 = Mandell | first1 = Gerald L. | last2 = Bennett | first2 = John E. (John Eugene) | last3 = Dolin | first3 = Raphael. | title = Mandell, Douglas, and Bennett's principles and practice of infectious disease | date = 2010 | publisher = Churchill Livingstone/Elsevier | location = Philadelphia, PA | isbn = 0-443-06839-9 | pages = }}</ref>
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| ===Imaging studies===
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| Although both [[MRI]] and [[CT]] scan may be used to help in the [[diagnosis]] of ''[[Listeria monocytogenes]]'' lesions, the [[MRI]] is a more [[sensitivity|sensitive]] method to detect ''listerial'' lesions in the [[cerebellum]], [[brainstem]] and [[cortex]].<ref name="pmid8507761">{{cite journal| author=Armstrong RW, Fung PC| title=Brainstem encephalitis (rhombencephalitis) due to Listeria monocytogenes: case report and review. | journal=Clin Infect Dis | year= 1993 | volume= 16 | issue= 5 | pages= 689-702 | pmid=8507761 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=8507761 }} </ref> 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.
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| 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]].
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| ===Anton Test===
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| * Used in the identification of [[Listeria monocytogenes]]
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| * Instillation of a culture into the [[conjunctiva]]l sac of a rabbit or guinea pig causes severe keratoconjunctivitis within 24 hours.<ref>{{cite web|url=http://medical-dictionary.thefreedictionary.com/Anton+test |title=Anton test - definition of Anton test in the Medical dictionary - by the Free Online Medical Dictionary, Thesaurus and Encyclopedia |publisher=Medical-dictionary.thefreedictionary.com |accessdate=2013-08-05}}</ref><ref>{{cite web|url=http://www.whonamedit.com/synd.cfm/197.html |title=Anton's eye test |publisher=Whonamedit |accessdate=2013-08-05}}</ref>
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| ===Cell Culture===
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| * [[Listeria]] grows on media such as Mueller-Hinton agar.<ref>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</ref>
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| * 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 the colonies.
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| * Isolation can be enhanced if the tissue is kept at 4°C for some days before inoculation into bacteriologic media.
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| * The [[motility]] at room temperature and [[hemolysin]] production are primary findings that help differentiate [[listeria]] from coryneform bacteria.
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| ==References== | | ==References== |
| {{Reflist|2}} | | {{Reflist|2}} |
| [[Category:Bacterial diseases]]
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| [[Category:Disease]]
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| [[Category:Infectious disease]]
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| {{WH}} | | {{WH}} |
| {{WS}} | | {{WS}} |
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| | [[Category:Emergency mdicine]] |
| | [[Category:Disease]] |
| | [[Category:Up-To-Date]] |
| | [[Category:Infectious disease]] |
| | [[Category:Neurology]] |
| | [[Category:Gastroenterology]] |