Difference between revisions of "Listeria species"
Jump to navigation
Jump to search
| Line 8: | Line 8: | ||
*''L. monocytogenes'' and ''L. ivanovii'' are pathogens | *''L. monocytogenes'' and ''L. ivanovii'' are pathogens | ||
*Carried by sheep and goats and shed in faeces and milk especially during stress | *Carried by sheep and goats and shed in faeces and milk especially during stress | ||
| − | *Can cause septicaemia, encephalitis and | + | *Can cause septicaemia, encephalitis, abortion and endophthalmitis in ruminants |
*Outbreaks of listeriosis often linked to silage feeding | *Outbreaks of listeriosis often linked to silage feeding | ||
| Line 16: | Line 16: | ||
*Small Gram negative rods | *Small Gram negative rods | ||
*Catalase positive, oxidase negative | *Catalase positive, oxidase negative | ||
| − | * | + | *Tumbling motility |
*Facultative anaerobes | *Facultative anaerobes | ||
*''L. monocytogenes is haemolytic on blood agar due to a cytolytic protein, listeriolysin; grows at range of pH values and temperatures | *''L. monocytogenes is haemolytic on blood agar due to a cytolytic protein, listeriolysin; grows at range of pH values and temperatures | ||
| Line 40: | Line 40: | ||
===Clinical infections=== | ===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 | ||
| + | **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 | ||
| + | *Septicaemic listeriosis: | ||
| + | **Incubation perios 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 | ||
| + | |||
| + | *''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 07:36, 20 July 2008
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
Characteristics
- Small Gram negative rods
- Catalase positive, oxidase negative
- Tumbling motility
- Facultative anaerobes
- 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
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
- 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
- Septicaemic listeriosis:
- Incubation perios 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
- 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