Listeria
&
Erysipelothrix
Filename: Listeria.ppt
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Outline
 Microbes
– Corynebacterium,Listeria, Erysipelothrix
 Diseases
– Diphtheria,Listeriosis, Erysipeloid
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Listeriosis
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Listeria monocytogenes
short , motile,non-spore - forming, Grm + rods,
- hemolytic, looks like Group B
streptococcus but group B is catalase neg
and non-motile.
found in wild and domestic animals excreted
into soils
healthy human carriers 5-10 %
source of infection is food and animal contact.
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Listeria Infections
Neonatal sepsis or meningitis
 Spontaneous abortion or still birth
 Sepsis or meningitis in immunocompromised
patients
 Puerperal sepsis
Persons at risk: Pregnant, post partum, new born,
organ transplants

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Listeriosis
 Disease
of humans
– Sepsis
– Meningitis + encephalitis
 25%
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mortality
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Listeria Pathogenesis
 Ingested
raw contaminated food
 Penetrates cell of intestine
 common event
 most have T cells
 Facultative intracellular pathogen
 Immunocompromised host
 Transmitted congenitally
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Listeriosis Diagnosis
 Monocytosis
– Peripheral blood & cerebrospinal fluid
 Gram
stain
– Gram positive rods in CFS
 Culture
– Blood, CSF, skin lesions
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Listeria: Virulence Factors
Internalin an invasion factor controlled by
the inl A gene
 The organisms are taken into the cell by
forced phagocytosis, become enclosed in
a vesicle and rupture it.
 Listeriolysin - alpha hemolysis hly gene.
 Lecithinase - hemolysin Phospholipase

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Listeria: Food poisoning
MILK and dairy products. This species
grows at refrigerator temp. 5-12o C
Isolated by cold enrichment.
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Test for Listeria in Milk
Add fluorescent-labelled antibodies specific for
Listeria monocytogenes to milk
Pass through a flow cytometer. fluid is passed
through a small opening
Listeria detected by a laser beam
NO CULTURE NEEDED!!!
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Listeriosis Prevention
Persons at risk
 avoid soft cheeses and unpasteurized
milk and processed meat that cannot be
cooked.
 thoroughly cook all meats especially
hot dogs
– left over meat should be cooked to
steaming.
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Listeriosis Control
 Hygienic
food processing
– contaminated vegetables
– vinegar in salads
 Antimicrobial
agents
– Not cephalosporins
– Ampicllin + aminoglycoside
– bacteriostatic
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Erysipeloid
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Erysipelothrix pathogenesis
 Skin
lesions
– fingers or hand
– violet or wine coloured
 Occasionally
septicemia
– endocarditis
– afebrile arthritis
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Erysipelothrix rhusiopathiae
 Gram
positive rods
 Grow aerobically
– prefer 7% carbon dioxide
 Non
motile
 Non hemolytic
 Produce hydrogen sulfide
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Erysipelothrix
Epidemiology
 Found
in mammals, poultry & fish
 Farmers, vets, slaughterhouse workers,
fish handlers
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Erysipelothrix
Diagnosis & Control
 Diagnosis
– Typical lesions
– Occupation
– Blood culture if sepsis
 Control
– Self limiting
– Penicillin if complications
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The End
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Performance Objectives
Key terms, concepts
short answers
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Key Terms
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Key Terms
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Key Organisms
 Corynebacterium
 Listeria
 Erysipelothrix
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Key Concepts
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Epidemiology of Listeriosis
 Disease/bacterial
factors
 Transmission
 Who
is at risk
 Geography/ season
 Incidence
 Modes of control
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Short Answers
 Construct
a table of the virulence factors
associated with listeriosis and the biological
activity of each
 Describe the clinical manifestations of
listeriosis
 Construct a table listing the common
Corynebacteria and the associated diseases.
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