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Listeria&

ErysipelothrixFilename: Listeria.ppt

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Outline

Microbes– Corynebacterium,Listeria, Erysipelothrix

Diseases– Diphtheria,Listeriosis, Erysipeloid

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Listeriosis

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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.

Listeria monocytogenes

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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% 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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MILK and dairy products. This species grows at refrigerator temp. 5-12o C

Isolated by cold enrichment.

Listeria: Food poisoning

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Test for Listeria in MilkAdd 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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ErysipelothrixDiagnosis & 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.