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{{Listeriosis}}
{{Listeriosis}}
{{Seealso|Listeria monocytogenes|Listeria ivanovii}}


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{{CMG}}; {{AE}} {{YD}}; {{SSK}}


==Overview==
==Overview==
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==Historical Perspective==
==Historical Perspective==
''[[Listeria monocytogenes]]'' (formerly ''Bacterium monocytogenes'') was isolated in 1926 by Everitt Murray and renamed [[Listeria monocytogenes]] in 1940 after [[Joseph Lister]], in honor of his discovery of sterilization to prevent surgical infection. Initially described as a [[bacteria]] of laboratory animals, the first human cases were described in 1929 by Nyfeldt, in Denmark.
''[[Listeria monocytogenes]]'' (formerly ''Bacterium monocytogenes'') was first isolated in 1926 by Everitt Murray. The organism was renamed [[Listeria monocytogenes]] in 1940 in honor of [[Joseph Lister]]. Initially described as a bacteria of laboratory animals, the first human cases were described in 1929 by Nyfeldt in Denmark.


==Classification==
==Classification==
Clinical [[syndromes]] caused by ''[[Listeria monocytogenes]]'' include: [[infection]] in pregnancy, neonatal [[infection]], [[bacteremia]], [[central nervous system infection]] ([[meningitis]], [[encephalitis]], rhombencephalitis, [[brain abscess]], [[spinal cord]] [[infection]]), [[endocarditis]], localized [[infection]], and [[febrile]] [[gastroenteritis]].
Listeriosis may be classified according to the clinical syndrome into the following: neonatal listeriosis, genitourinary infection, gastroenteritis, central nervous system infection, endocarditis, bacteremia, and localized infection.


==Pathophysiology==
==Pathophysiology==
''[[Listeria monocytogenes]]'' is able to enter de body through the [[gastrointestinal]] lining, causing [[infection]] in otherwise [[sterile]] sites. The [[pathogenesis]] of ''L. monocytogenes'' is centered on its ability to survive and multiply within [[phagocytic]] host [[cells]], which it uses to travel to difference sites in the body. ''[[Listeria monocytogenes]]'' is transmitted through contaminated food and causes [[infection]] particularly in [[immunosuppressed]] patients, elderly, and pregnant women. Microscopically, the [[infected]] sites are characterized by the occurrence of [[inflammation]], with [[exudate]] and presence of multiple [[neutrophils]].
''Listeria'' is commonly transmitted via contaminated food or via vertical transmission from mother to fetus. Following transmission, ''Listeria'' encodes thermoregulated [[virulence factor]] in the human host, invades the intestinal epithelium, and multiplies intracellularly within [[phagocytic]] phagolyosomes. It is able to escape lyosomal destruction by secreting phospholipases and listeriolysin O, a [[hemolysin]] that is responsible for lysis the [[vacuole]]'s membrane. ''Listeria'' then migrates between cells by forming protrusions called filopods or "rockets" using polymerized actin and Gelsolin, an actin-binding protein. Microscopically, tissue infected with ''Listeria monocytogenes'' often demonstrates microscopic features of [[inflammation]], exudate formation, and neutrophilia. In prolonged [[infections]], macrophages may be abundantly present in tissue specimens, and granuloma formation may occur.


==Causes==
==Causes==
''Listeria monocytogenes'' is a [[Gram-positive]], facultative [[intracellular]] parasite, [[anaerobe]], [[spore|nonsporulating]] [[bacillus]]. [[Motility|Motile]] via [[flagella]], ''L. monocytogenes'' can move within [[Eukaryote|eukaryotic]] [[cells]] by explosive [[polymerization]] of [[actin]] filaments (known as ''comet tails'' or ''actin rockets''). The name ''monocitogenes'' derives from the strong [[monocytic]] activity this organism produces in rabbits, which however, does not happen in humans.<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> Different [[strains]] of the [[bacteria]] show different [[pathogenic]] [[tropism]]s towards different [[tissues]]. It is commonly found in soil, water, vegetation and fecal material.<ref name=WHO>{{cite web | title = Risk assessment of Listeria monocytogenes in ready-to-eat foods | url = http://whqlibdoc.who.int/publications/2004/9241562625_part1.pdf }}</ref>
Listeriosis is caused by the bacterium ''Listeria monocytogenes'', a flagellated, [[catalase-positive]], facultative [[intracellular]], [[anaerobe|anaerobic]], [[spore|nonsporulating]], [[Gram-positive]] [[bacillus]]. ''Listeria'' is commonly found in soil, water, vegetation and fecal material.


==Differential Diagnosis==
==Differential Diagnosis==
Listeriosis is associated with different clinical [[syndromes]]; therefore, it should be differentiated from a wide range of diseases. Differential diagnoses of listeriosis include [[febrile]] [[gastroenteritis]], parenchymal brain [[infections]], subcortical [[brain abscess]]es, and  [[fever]] during the last trimester of pregnancy.<ref name="Lorber1997">{{cite journal|last1=Lorber|first1=B.|title=Listeriosis|journal=Clinical Infectious Diseases|volume=24|issue=1|year=1997|pages=1–11|issn=1058-4838|doi=10.1093/clinids/24.1.1}}</ref>
Listeriosis is associated with more than one clinical [[syndrome]]. It must be differentiated from other infections that cause fever and systemic/localized symptoms (either [[CNS disease]], [[gastroenteritis]], genitourinary disease, [[endocarditis]], or [[bacteremia]]), such as ''[[E. coli]]'', ''[[Neisseria]] spp.'', ''[[Streptococcus]] spp.'', ''[[Staphylococcus]] spp.'', ''[[Shigella]]'', ''[[Salmonella]]'', ''[[Campylobacter]]'', ''[[Serratia]] spp.'', or ''[[Haemophilus]] spp.'', [[mononucleosis]], or [[tuberculosis]]. ''Listeria monocytogenes'' must also be differentiated from other organisms that are morphologically similar, such as pneumococci, diphtheroids, or ''Haemophilus spp.'' . Differential diagnosis of listeriosis additionally includes hematologic malignancies (such as [[leukemia]] or [[lymphoma]]), [[thyroid disease]], [[drug fever]], [[vasculitis|vasculitides]], or [[rheumatologic disease]]s.


==Epidemiology and Demographics==
==Epidemiology and Demographics==
In 2013, the average annual incidence of listeriosis in the United States was 0.26 cases per 100,000 individuals.<ref name=MM>CDC. [http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6315a3.htm Incidence and Trends of Infection with Pathogens Transmitted Commonly Through Food — Foodborne Diseases Active Surveillance Network], 10 U.S. Sites, 2006–2013. MMWR Morb Mortal Wkly Rep. 2014;63(15);328-332</ref> The disease has a worldwide distribution, with sporadic [[incidence]] affecting mostly [[immunosuppressed]] patients, pregnant women, neonates, and elderly subjects.<ref name=CDC>{{cite web | title = Listeria Stattistics | url = http://www.cdc.gov/listeria/statistics.html }}</ref>
The annual incidence of listeriosis in the United States is approximately 0.2-0.3 cases per 100,000 individuals.<ref name=MM>CDC. [http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6315a3.htm Incidence and Trends of Infection with Pathogens Transmitted Commonly Through Food — Foodborne Diseases Active Surveillance Network], 10 U.S. Sites, 2006–2013. MMWR Morb Mortal Wkly Rep. 2014;63(15);328-332</ref> The incidence of listeriosis is higher among females (especially pregnant women), neonates, elderly individuals, and Hispanic individuals. Listeriosis has a worldwide distribution in both developed and developing countries.<ref name=CDC>{{cite web | title = Listeria Stattistics | url = http://www.cdc.gov/listeria/statistics.html }}</ref>


==Risk Factors==
==Risk Factors==
The ingestion of uncooked meats and vegetables, unpasteurized (raw) milk and cheeses, processed (or ready-to-eat) meats, and smoked seafood is a risk factor for listeriosis.<ref name=Sources>Listeria (Listeriosis) Sources. CDC.gov accessed on 7/25/2014 [http://www.cdc.gov/listeria/sources.html]</ref>  [[Immunosuppressed]] patients, neonates, pregnant women, and elderly patients have higher risk of contracting [[listeriosis]].<ref name="Lorber-1997">{{Cite journal  | last1 = Lorber | first1 = B. | title = Listeriosis. | journal = Clin Infect Dis | volume = 24 | issue = 1 | pages = 1-9; quiz 10-1 | month = Jan | year = 1997 | doi =  | PMID = 8994747 }}</ref>
Risk factors in the development of listeriosis include ingestion of uncooked meats and vegetables, unpasteurized (raw) milk and cheeses, processed (or ready-to-eat) meats, and smoked seafood.<ref name=Sources>Listeria (Listeriosis) Sources. CDC.gov accessed on 7/25/2014 [http://www.cdc.gov/listeria/sources.html]</ref>  Populations at higher risk of developing listeriosis include [[immunosuppressed]] patients (e.g. [[transplant]] recipients, patients with history of [[splenectomy]], patients receiving [[immunosuppressive therapy]], or patients with advanced [[diabetes]], [[kidney disease|kidney]]/ [[liver disease]], or active [[malignancy]]),  [[neonates]], pregnant women, and elderly patients.<ref name="Lorber-1997">{{Cite journal  | last1 = Lorber | first1 = B. | title = Listeriosis. | journal = Clin Infect Dis | volume = 24 | issue = 1 | pages = 1-9; quiz 10-1 | month = Jan | year = 1997 | doi =  | PMID = 8994747 }}</ref>


==Natural History, Complications and Prognosis==
==Natural History, Complications and Prognosis==
[[Listeriosis]] is commonly [[transmission|transmitted]] through contaminated food. The clinical presentation of the disease depends on the baseline health status of the patient. Although [[asymptomatic]] carriers may be identified, the disease is commonly manifested as [[febrile]] [[gastroenteritis]]. Other more invasive manifestations include [[sepsis]] of unknown origin, [[bacteremia]], [[CNS infection|central nervous system (CNS) infection]], [[endocarditis]], and focal [[infections]]. Possible [[complications]] of [[listeriosis]] include [[acute respiratory distress syndrome]] ([[ARDS]]), [[rhabdomyolysis]], [[acute renal failure]], and [[pneumonia]]. The [[prognosis]] of [[listeriosis]] depends on the health status of the host, where healthy older children and adults show the lowest [[death rate]].<ref name=CDC>{{cite web | title = Listeria | url = http://www.cdc.gov/listeria/definition.html }}</ref>
Following transmission, the majority of healthy patients do not develop clinical manifestations or may develop a mild, transient bacteremia. Early clinical manifestations (usually fever) typically develop early within 24 hours of transmission. If left untreated, patients typically progress within 1-90 days to develop ''Listeria''-associated complications, including [[bacteremia]], [[abscess]] formation, [[pneumonia]], [[ARDS]], [[acute kidney injury]], and [[CNS impairment]]. Among healthy children and young adults, the prognosis of listeriosis is generally good. Prognosis is poorer among high-risk populations, who are more likely to develop complications and death even with prompt management.


==Diagnosis==
==Diagnosis==
===History and Symptoms===
===History and Symptoms===
The clinical manifestation of [[listeriosis]] is host-dependent. [[Immunocompetent]] persons may experience acute [[febrile]] [[gastroenteritis]] or no [[symptoms]].  Among older adults and [[immunocompromised]] persons, the most common clinical presentations are [[septicemia]] and [[meningitis]]. Pregnant women may experience a mild [[flu]]-like illness, followed by fetal loss, or [[bacteremia]] and [[meningitis]] in the newborns.
Fever is the most common symptom of listeriosis. Other symptoms develop on location of the infection: Patients with [[gastroenteritis]] may develop [[watery diarrhea]], [[abdominal pain]], [[vomiting]], and [[headache]]. Patients with CNS infection may develop symptoms of [[meningitis]], [[encephalitis]], [[cerebritis]], rhombencephalitis, or spinal cord infection, such as [[headache]], [[back pain]], [[neck pain]], [[photophobia]], [[phonophobia]], [[deafness]], [[confusion]], [[ataxia]], [[seizures]], and neurological impairment.


===Physical Examination===
===Physical Examination===
The findings on the [[physical examination]] depend on the clinical manifestation of listeriosis (febrile [[gastroenteritis]], [[sepsis]], infection in pregnancy, [[central nervous system]] infection, or [[endocarditis]]). Common findings include [[fever]], [[tachycardia]], [[pallor]].  Signs of [[neurological]] involvement may range from [[altered mental state]], to [[paralysis]], [[respiratory failure]], and [[coma]].
The findings on the [[physical examination]] depend on the clinical manifestation of listeriosis. Common findings include [[fever]], [[tachycardia]], [[pallor]], and [[abdominal tenderness]].  Signs of [[neurological]] involvement may include [[altered mental state]], [[paralysis]], [[respiratory failure]], and [[coma]].


===Laboratory Findings===
===Laboratory Findings===
 
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 sample]]s, 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. [[Serology|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.<ref name=CDC>{{cite web | title = Listeria | url = http://www.cdc.gov/listeria/diagnosis.html }}</ref>
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]]). Stool samples are of limited use and are not recommended. Listeria monocytogenes can be isolated readily on routine media, but care must be taken to distinguish this organism from other [[Gram-positive]] rods, particularly [[diphtheroid]]s. Selective enrichment media improve rates of isolation from contaminated specimens. The cultures take 1-2 days for growth. 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. There is no clinical value in performing laboratory testing on asymptomatic patients, even if higher risk.<ref name=CDC>{{cite web | title = Listeria | url = http://www.cdc.gov/listeria/diagnosis.html }}</ref>


===MRI===
===MRI===
Although both [[MRI]] and [[CT]] scan may be used to help in the [[diagnosis]] of ''[[Listeria monocytogenes]]'' lesions, [[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>  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 ''[[Listeria monocytogenes]]'', it is helpful to use contrast [[MRI]] in all patients presenting with listerial [[meningitis]], listerial [[bacteremia]], [[CNS]] signs and symptoms or suspicion of intracranial [[listeriosis]].
Brain [[MRI]] may be helpful in the [[diagnosis]] of ''[[Listeria monocytogenes]]'' brain lesions. Findings on [[MRI]] suggestive of listeriosis include 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>  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.  With a high pre-test probability, [[brainstem]] involvement on MRI is strongly suggestive of listeriosis. Contrast [[MRI]] is recommended among all patients presenting with listerial [[meningitis]], listerial [[bacteremia]], suggestive [[CNS]] signs and symptoms or upon suspicion of intracranial [[listeriosis]].


===Other Diagnostic Studies===
===Other Diagnostic Studies===
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 exist but they are unreliable and not recommended at the present time.
Additional studies for the diagnosis of listeriosis are not recommended.


==Treatment==
==Treatment==
===Medical Therapy===
===Medical Therapy===
 
All patients with listeriosis require antibiotic therapy. [[Ampicillin]], with or without [[gentamicin]], is the antibiotic of choice for the treatment of listeriosis. Patients intolerant to [[penicillin]]s may be managed with [[TMP/SMZ|trimethoprim-sulfamethoxazole]]. Duration of therapy depends on the clinical syndrome and may range from several days in non-complicated gastroenteritis to 6 weeks in endocarditis or encephalitis. Listerial [[gastroenteritis]] is frequently self-limited among healthy adults, but a short course of oral [[ampicillin]] may be considered among immunocompromised or pregnant individuals or those who have ingested food implicated in outbreaks. Non-gastroenteritis listeriosis often require hospitalization and intravenous (IV) antibiotic therapy.
[[Ampicillin]], with or without [[gentamicin]], is the preferred antibiotic for the treatment of listeriosis. Patients intolerant to [[penicillin]]s may be managed with [[TMP/SMZ|trimethoprim-sulfamethoxazole]]. The suggested minimum duration of therapy depends on the clinical syndrome. Listerial [[gastroenteritis]] is frequently self-limited but a short course of oral [[ampicillin]] may be considered in individuals with impaired [[cell-mediated immunity]] or those who have ingested food implicated in outbreaks. Listeria [[bacteremia]] requires at least 2 weeks of treatment, [[meningitis]] 3 weeks, [[endocarditis]] 4 to 6 weeks, and [[brain abscess]] or [[encephalitis|rhombencephalitis]] 6 weeks.


===Surgery===
===Surgery===
The treatment of [[listeriosis]] is based on an adequate [[antibiotic]] regimen. Surgery may be indicated for [[complications]] of [[listeriosis]], such as [[central nervous system]] ([[CNS]]) [[complications]] or [[heart valve|valve]] damage caused by [[endocarditis]].
Surgery is not usually recommended among patients with listeriosis. Surgery may be indicated in cases of Listeria-associated complications, such as abscess formation requiring abscess drainage or advanced endocarditis require valve repair.


===Primary Prevention===
===Primary Prevention===
General recommendations for the primary prevention of infection with Listeria include appropriately washing and handling of food, maintaining a clean and safe kitchen and environment, cooking meat and poultry thoroughly, safely storing foods, and choosing safe foods.  In addition to the general recommendations on how to prevent an infection with Listeria, there are additional recommendations specifically for persons who are at higher risk, such as pregnant women, elderly, and individuals with compromised [[immune systems]]. Besides the [[primary prevention]] measures, there is no [[prophylaxis]] for [[listeriosis]].
General recommendations for the primary prevention of infection with Listeria include appropriately washing and handling of food, maintaining a clean and safe kitchen and environment, cooking meat and poultry thoroughly, safely storing foods, and choosing safe foods.  In addition to the general recommendations on how to prevent an infection with Listeria, there are additional recommendations specifically for persons who are at higher risk, such as pregnant women, elderly, and individuals with compromised immune status. There is no vaccine against listeriosis. Pharmacologic prophylactic measures against listeriosis are not helpful.


==References==
==References==
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [2]; Associate Editor(s)-in-Chief: Yazan Daaboul, M.D.; Serge Korjian M.D.

Overview

Listeriosis is a bacterial infection caused by a gram-positive, motile bacterium, Listeria monocytogenes.[1] Listeriosis is relatively rare and occurs primarily in newborn infants, elderly patients, and patients who are immunocompromised.[2]

Historical Perspective

Listeria monocytogenes (formerly Bacterium monocytogenes) was first isolated in 1926 by Everitt Murray. The organism was renamed Listeria monocytogenes in 1940 in honor of Joseph Lister. Initially described as a bacteria of laboratory animals, the first human cases were described in 1929 by Nyfeldt in Denmark.

Classification

Listeriosis may be classified according to the clinical syndrome into the following: neonatal listeriosis, genitourinary infection, gastroenteritis, central nervous system infection, endocarditis, bacteremia, and localized infection.

Pathophysiology

Listeria is commonly transmitted via contaminated food or via vertical transmission from mother to fetus. Following transmission, Listeria encodes thermoregulated virulence factor in the human host, invades the intestinal epithelium, and multiplies intracellularly within phagocytic phagolyosomes. It is able to escape lyosomal destruction by secreting phospholipases and listeriolysin O, a hemolysin that is responsible for lysis the vacuole's membrane. Listeria then migrates between cells by forming protrusions called filopods or "rockets" using polymerized actin and Gelsolin, an actin-binding protein. Microscopically, tissue infected with Listeria monocytogenes often demonstrates microscopic features of inflammation, exudate formation, and neutrophilia. In prolonged infections, macrophages may be abundantly present in tissue specimens, and granuloma formation may occur.

Causes

Listeriosis is caused by the bacterium Listeria monocytogenes, a flagellated, catalase-positive, facultative intracellular, anaerobic, nonsporulating, Gram-positive bacillus. Listeria is commonly found in soil, water, vegetation and fecal material.

Differential Diagnosis

Listeriosis is associated with more than one clinical syndrome. It must be differentiated from other infections that cause fever and systemic/localized symptoms (either CNS disease, gastroenteritis, genitourinary disease, endocarditis, or bacteremia), such as E. coli, Neisseria spp., Streptococcus spp., Staphylococcus spp., Shigella, Salmonella, Campylobacter, Serratia spp., or Haemophilus spp., mononucleosis, or tuberculosis. Listeria monocytogenes must also be differentiated from other organisms that are morphologically similar, such as pneumococci, diphtheroids, or Haemophilus spp. . Differential diagnosis of listeriosis additionally includes hematologic malignancies (such as leukemia or lymphoma), thyroid disease, drug fever, vasculitides, or rheumatologic diseases.

Epidemiology and Demographics

The annual incidence of listeriosis in the United States is approximately 0.2-0.3 cases per 100,000 individuals.[3] The incidence of listeriosis is higher among females (especially pregnant women), neonates, elderly individuals, and Hispanic individuals. Listeriosis has a worldwide distribution in both developed and developing countries.[4]

Risk Factors

Risk factors in the development of listeriosis include ingestion of uncooked meats and vegetables, unpasteurized (raw) milk and cheeses, processed (or ready-to-eat) meats, and smoked seafood.[5] Populations at higher risk of developing listeriosis include immunosuppressed patients (e.g. transplant recipients, patients with history of splenectomy, patients receiving immunosuppressive therapy, or patients with advanced diabetes, kidney/ liver disease, or active malignancy), neonates, pregnant women, and elderly patients.[6]

Natural History, Complications and Prognosis

Following transmission, the majority of healthy patients do not develop clinical manifestations or may develop a mild, transient bacteremia. Early clinical manifestations (usually fever) typically develop early within 24 hours of transmission. If left untreated, patients typically progress within 1-90 days to develop Listeria-associated complications, including bacteremia, abscess formation, pneumonia, ARDS, acute kidney injury, and CNS impairment. Among healthy children and young adults, the prognosis of listeriosis is generally good. Prognosis is poorer among high-risk populations, who are more likely to develop complications and death even with prompt management.

Diagnosis

History and Symptoms

Fever is the most common symptom of listeriosis. Other symptoms develop on location of the infection: Patients with gastroenteritis may develop watery diarrhea, abdominal pain, vomiting, and headache. Patients with CNS infection may develop symptoms of meningitis, encephalitis, cerebritis, rhombencephalitis, or spinal cord infection, such as headache, back pain, neck pain, photophobia, phonophobia, deafness, confusion, ataxia, seizures, and neurological impairment.

Physical Examination

The findings on the physical examination depend on the clinical manifestation of listeriosis. Common findings include fever, tachycardia, pallor, and abdominal tenderness. Signs of neurological involvement may include altered mental state, paralysis, respiratory failure, and coma.

Laboratory Findings

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.[4]

MRI

Brain MRI may be helpful in the diagnosis of Listeria monocytogenes brain lesions. Findings on MRI suggestive of listeriosis include lesions in the cerebellum, brainstem, and cortex.[7] 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. With a high pre-test probability, brainstem involvement on MRI is strongly suggestive of listeriosis. Contrast MRI is recommended among all patients presenting with listerial meningitis, listerial bacteremia, suggestive CNS signs and symptoms or upon suspicion of intracranial listeriosis.

Other Diagnostic Studies

Additional studies for the diagnosis of listeriosis are not recommended.

Treatment

Medical Therapy

All patients with listeriosis require antibiotic therapy. Ampicillin, with or without gentamicin, is the antibiotic of choice for the treatment of listeriosis. Patients intolerant to penicillins may be managed with trimethoprim-sulfamethoxazole. Duration of therapy depends on the clinical syndrome and may range from several days in non-complicated gastroenteritis to 6 weeks in endocarditis or encephalitis. Listerial gastroenteritis is frequently self-limited among healthy adults, but a short course of oral ampicillin may be considered among immunocompromised or pregnant individuals or those who have ingested food implicated in outbreaks. Non-gastroenteritis listeriosis often require hospitalization and intravenous (IV) antibiotic therapy.

Surgery

Surgery is not usually recommended among patients with listeriosis. Surgery may be indicated in cases of Listeria-associated complications, such as abscess formation requiring abscess drainage or advanced endocarditis require valve repair.

Primary Prevention

General recommendations for the primary prevention of infection with Listeria include appropriately washing and handling of food, maintaining a clean and safe kitchen and environment, cooking meat and poultry thoroughly, safely storing foods, and choosing safe foods. In addition to the general recommendations on how to prevent an infection with Listeria, there are additional recommendations specifically for persons who are at higher risk, such as pregnant women, elderly, and individuals with compromised immune status. There is no vaccine against listeriosis. Pharmacologic prophylactic measures against listeriosis are not helpful.

References

  1. Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed. ed.). McGraw Hill. ISBN 0-8385-8529-9.
  2. Hof H (1996). Listeria Monocytogenes in: Baron's Medical Microbiology (Baron S et al, eds.) (4th ed. ed.). Univ of Texas Medical Branch. (via NCBI Bookshelf) ISBN 0-9631172-1-1.
  3. CDC. Incidence and Trends of Infection with Pathogens Transmitted Commonly Through Food — Foodborne Diseases Active Surveillance Network, 10 U.S. Sites, 2006–2013. MMWR Morb Mortal Wkly Rep. 2014;63(15);328-332
  4. 4.0 4.1 "Listeria Stattistics".
  5. Listeria (Listeriosis) Sources. CDC.gov accessed on 7/25/2014 [1]
  6. Lorber, B. (1997). "Listeriosis". Clin Infect Dis. 24 (1): 1–9, quiz 10-1. PMID 8994747. Unknown parameter |month= ignored (help)
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