Difference between revisions of "Listeria species"
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| − | + | {{review}} | |
| + | |||
| + | {{toplink | ||
| + | |backcolour = | ||
| + | |linkpage =Bacteria | ||
| + | |linktext =BACTERIA | ||
| + | |pagetype=Bugs | ||
| + | }} | ||
| + | <br> | ||
| + | ===Overview=== | ||
| + | |||
| + | *6 species | ||
| + | *Saprophytes in soil | ||
| + | *''L. monocytogenes'' and ''L. ivanovii'' are pathogens | ||
| + | *Carried by sheep and goats and shed in faeces and milk especially during stress | ||
| + | *Can cause septicaemia, encephalitis, abortion and endophthalmitis in ruminants | ||
| + | *Outbreaks of listeriosis often linked to silage feeding | ||
| + | *Occurs in North and East Europe and North America | ||
| + | |||
| + | |||
| + | ===Characteristics=== | ||
| + | |||
| + | *Small Gram positive rods | ||
| + | *Catalase positive, oxidase negative | ||
| + | *Tumbling motility | ||
| + | *Facultative anaerobes | ||
| + | *Intracellular pathogens | ||
| + | *''L. monocytogenes is haemolytic on blood agar due to a cytolytic protein, listeriolysin; grows at range of pH values and temperatures | ||
| + | *''L. ivanovii produces strong haemolytic zone | ||
| + | *Small, smooth, transparent colonies after 24 hours incubation | ||
| + | *Grow on non-enriched media | ||
| + | |||
| + | ===Pathogenesis and pathogenicity=== | ||
| + | |||
| + | *Infection by ingestion of contaminated feed | ||
| + | *Bacteria penetrate M cells in intestinal Peyer's patches | ||
| + | *Spread to tissues via blood and lymph | ||
| + | *Transplacental transmission in pregnant animals | ||
| + | *Bacteria may gain entry via breaks in oral or nasal mucosa, migrate in cranial nerves to cause neural signs | ||
| + | *Causes formation of microabscesses and perivascular lymphocytic cuffs in brainstem | ||
| + | *''L. monocytogenes'' can replicate within phagocytic and non-phagocytic cell, and pass between cells without being exposed to the immune system | ||
| + | *Surface proteins known as internalins allow adherence and uptake of the bacteria into cells | ||
| + | *Listeriolysin produced by virulent strains destroys membranes of phagocytic vacuoles, releasing the bacteria into the cytoplasm | ||
| + | *Listeria are motile in the cytoplasm | ||
| + | *Bacteria induce formation of pseudopod projections in the cytoplasmic membrane, which are taken up with the bacteria into adjacent cells | ||
| + | *Cell-mediated immune response required for protection | ||
| + | |||
| + | |||
| + | ===Clinical infections=== | ||
| + | |||
| + | *Outbreaks of listeriosis caused by ''L. moncytogenes'' seasonal and linked to silage feeding | ||
| + | *Replicates in poor quality silage where the pH excedes 5.5 | ||
| + | *Animals highly susceptible during pregnancy due to lowered cell-mediated immunity | ||
| + | *Neural listeriosis: | ||
| + | **Incubation period 14-40 days | ||
| + | **Meningoencephalitis | ||
| + | **Dullness, circling, head tilt, facial paralysis, drool saliva, droop of eyelid and ear | ||
| + | **Exposure keratitis | ||
| + | **Fever during early stages | ||
| + | **Recumbency and death within a few days in sheep and goats | ||
| + | **Abortion up to 12 days after infection in cattle; usually recover but may get septicaemia | ||
| + | *Septicaemic listeriosis: | ||
| + | **Incubation period 2-3 days | ||
| + | **Lambs and occasionally pregnant sheep | ||
| + | **Occurs in newborn piglets, foals, poultry, adult sheep | ||
| + | *Keratoconjunctivitis in cattle and sheep - direct contact with silage via eye | ||
| + | *Pneumonia, myocarditis, enodcarditis | ||
| + | *Zoonosis - consumption of contaminated unpasteurised milk; memingitis and meningoencephalitis; abortion | ||
| + | |||
| + | *''L. ivanovii causes sporadic abortion in sheep and cattle | ||
| + | *''L. innocua'' rarely causes ovine meningoencephalitis | ||
| + | |||
| + | ===Diagnosis=== | ||
| + | |||
| + | *Specimens should include CSF in neural cases, cotyledons in abortion, liver, spleen and blood in septicaemia | ||
| + | *Immunofluorescence using monoclonal antibodies | ||
| + | *Histology of brain demonstrates microabscesses and lymphocytic cuffing in brainstem | ||
| + | *Smears of cotyledons | ||
| + | *High protein and cell counts in CSF | ||
| + | *Isolation on blood and MacConkey agar | ||
| + | |||
| + | |||
| + | ===Treatment and control=== | ||
| + | |||
| + | *Ampicillin or amoxycillin in early stages of septicaemic listeriosis | ||
| + | *Sub-conjuntival antibiotics and corticosteroids for ocular listeriosis | ||
| + | *Avoid poor quality silage and discontinue silage-feeding in an outbreak | ||
Revision as of 21:08, 5 June 2009
 |
This article has been peer reviewed but is awaiting expert review. If you would like to help with this, please see more information about expert reviewing. |
|
Overview
- 6 species
- Saprophytes in soil
- L. monocytogenes and L. ivanovii are pathogens
- Carried by sheep and goats and shed in faeces and milk especially during stress
- Can cause septicaemia, encephalitis, abortion and endophthalmitis in ruminants
- Outbreaks of listeriosis often linked to silage feeding
- Occurs in North and East Europe and North America
Characteristics
- Small Gram positive rods
- Catalase positive, oxidase negative
- Tumbling motility
- Facultative anaerobes
- Intracellular pathogens
- L. monocytogenes is haemolytic on blood agar due to a cytolytic protein, listeriolysin; grows at range of pH values and temperatures
- L. ivanovii produces strong haemolytic zone
- Small, smooth, transparent colonies after 24 hours incubation
- Grow on non-enriched media
Pathogenesis and pathogenicity
- Infection by ingestion of contaminated feed
- Bacteria penetrate M cells in intestinal Peyer's patches
- Spread to tissues via blood and lymph
- Transplacental transmission in pregnant animals
- Bacteria may gain entry via breaks in oral or nasal mucosa, migrate in cranial nerves to cause neural signs
- Causes formation of microabscesses and perivascular lymphocytic cuffs in brainstem
- L. monocytogenes can replicate within phagocytic and non-phagocytic cell, and pass between cells without being exposed to the immune system
- Surface proteins known as internalins allow adherence and uptake of the bacteria into cells
- Listeriolysin produced by virulent strains destroys membranes of phagocytic vacuoles, releasing the bacteria into the cytoplasm
- Listeria are motile in the cytoplasm
- Bacteria induce formation of pseudopod projections in the cytoplasmic membrane, which are taken up with the bacteria into adjacent cells
- Cell-mediated immune response required for protection
Clinical infections
- Outbreaks of listeriosis caused by L. moncytogenes seasonal and linked to silage feeding
- Replicates in poor quality silage where the pH excedes 5.5
- Animals highly susceptible during pregnancy due to lowered cell-mediated immunity
- Neural listeriosis:
- Incubation period 14-40 days
- Meningoencephalitis
- Dullness, circling, head tilt, facial paralysis, drool saliva, droop of eyelid and ear
- Exposure keratitis
- Fever during early stages
- Recumbency and death within a few days in sheep and goats
- Abortion up to 12 days after infection in cattle; usually recover but may get septicaemia
- Septicaemic listeriosis:
- Incubation period 2-3 days
- Lambs and occasionally pregnant sheep
- Occurs in newborn piglets, foals, poultry, adult sheep
- Keratoconjunctivitis in cattle and sheep - direct contact with silage via eye
- Pneumonia, myocarditis, enodcarditis
- Zoonosis - consumption of contaminated unpasteurised milk; memingitis and meningoencephalitis; abortion
- L. ivanovii causes sporadic abortion in sheep and cattle
- L. innocua rarely causes ovine meningoencephalitis
Diagnosis
- Specimens should include CSF in neural cases, cotyledons in abortion, liver, spleen and blood in septicaemia
- Immunofluorescence using monoclonal antibodies
- Histology of brain demonstrates microabscesses and lymphocytic cuffing in brainstem
- Smears of cotyledons
- High protein and cell counts in CSF
- Isolation on blood and MacConkey agar
Treatment and control
- Ampicillin or amoxycillin in early stages of septicaemic listeriosis
- Sub-conjuntival antibiotics and corticosteroids for ocular listeriosis
- Avoid poor quality silage and discontinue silage-feeding in an outbreak