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Listeria
Listeria monocytogenes
Epidemiology
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Almost all cases of infection acquired through the
ingestion of contaminated food
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Pregnant women and immunocompromised patients are more
prone to infection with 2/3 of adult cases occurring in the
immunocompromised. However community acquired cases may occur spontaneously
in patients who have no underlying predisposing conditions
Pathogenicity
Can invade and survive within macrophages of the liver and
spleen as well as non-phagocytic cells (epithelial, hepatocellular, fibroblast
cell lines). As such the organisms are temporarily sheltered from host defence
mechanisms and they are able to grow and spread
Clinical features
Listerosis during pregnancy
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Early cases associated with septic abortion
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Most cases occur after 5 months gestation: premature
delivery of septic or stillborn infant
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Maternal flu like illness often precedes delivery by
2-14 days
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Fever and chills
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Fatigue, headache
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Myalgia
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Maternal listerosis can be transmitted to the fetus by
an ascending or transplacental route
Listerosis in non-pregnant adults
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Usually presents as meningitis or meningoencephalitis.
Occasionally as an isolated cerebritis
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Immunocompromised adults, particularly renal transplant
recipients
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Illness often subacute, similar to the pattern seen in
cryptococcal or tuberculous meningitis
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CSF: raised protein, moderate pleocytosis, (polymorphonuclear
cells>lymphocytes)
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High incidence of prolonged ataxia, hydrocephalus and
cerebellar atrophy.
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Brainstem encephalitis and brain abscesses also seen.
Good prognosis
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Focal infections include:
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Lymphadenitis
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Endocarditis
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Arthritis
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Osteomyelitis
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Peritonitis
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Acute cholecystitis
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Acute hepatitis
Management
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Tends to be susceptible to ampicillin, penicillin,
erythromycin and tetracycline.
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Uniformly highly resistant to cephalosporins
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In animal models combination of ampicillin with an
aminoglycoside resulted in significantly better eradication of organisms in
the spleen when compared with ampicillin alone
Listeriosis in pregnancy
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If amnionitis is present: ampicillin 4-6 g/day 6hrly IV
with an aminoglycoside.
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If amnionitis is not present or has subsided oral
amoxicillin 2-3 g/day is probably adequate.
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14 day course in both cases
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Erythromycin if patient allergic to penicillins. But
avoid estolate because increased liver toxicity in pregnancy
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Avoid trimethoprim-sulfamethoxazole because of
potential toxic effects if premature labour occurs and child is jaundiced
Listerosis in non-pregnant adults
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Meningitis: Ampicillin 200-400 mg/kg/day in 4-6 daily
doses for 3 weeks in combination with an aminoglycoside
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If response is delayed (>2 days) further
investigations including CT indicated to assess for presence of cerebritis,
abscess, brainstem encephalitis, or intracranial haemorrhage
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Treatment should be prolonged to 6 weeks if cerebral
pathology identified. If organism persists in CSF addition of rifampicin or
use of trimethoprim-sulfamethoxazole may be considered if organism is
sensitive in vitro.
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Vancomycin has been used successfully in patients who
are allergic to penicillin
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