Listeria&Erysipelothrix

Filename: Listeria.ppt

Outline

• Microbes
  • Corynebacterium,Listeria, Erysipelothrix

• Diseases
  • Diphtheria,Listeriosis, Erysipeloid

Listeriosis

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.

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

Listeriosis

• Disease of humans
  • Sepsis
  • Meningitis + encephalitis
    • 25% mortality

Listeria Pathogenesis

• Ingested raw contaminated food

• Penetrates cell of intestine

• common event

• most have T cells

• Facultative intracellular pathogen

• Immunocompromised host

• Transmitted congenitally

Listeriosis Diagnosis

• Monocytosis
  • Peripheral blood & cerebrospinal fluid

• Gram stain
  • Gram positive rods in CFS

• Culture
  • Blood, CSF, skin lesions

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

Listeria: Food poisoning

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

Isolated by cold enrichment.

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!!!

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.

Listeriosis Control

• Hygienic food processing
  • contaminated vegetables
  • vinegar in salads

• Antimicrobial agents
  • Not cephalosporins
  • Ampicllin + aminoglycoside
  • bacteriostatic

Erysipeloid

Erysipelothrix pathogenesis

• Skin lesions
  • fingers or hand
  • violet or wine coloured

• Occasionally septicemia
  • endocarditis
  • afebrile arthritis

Erysipelothrix rhusiopathiae

• Gram positive rods

• Grow aerobically
  • prefer 7% carbon dioxide

• Non motile

• Non hemolytic

• Produce hydrogen sulfide

Erysipelothrix Epidemiology

• Found in mammals, poultry & fish

• Farmers, vets, slaughterhouse workers, fish handlers

ErysipelothrixDiagnosis & Control

• Diagnosis
  • Typical lesions
  • Occupation
  • Blood culture if sepsis

• Control
  • Self limiting
  • Penicillin if complications

The End

Performance Objectives

Key terms, concepts

short answers

Key Terms

Key Terms

Key Organisms

• Corynebacterium

• Listeria

• Erysipelothrix

Key Concepts

Epidemiology of Listeriosis

• Disease/bacterial factors

• Transmission

• Who is at risk

• Geography/ season

• Incidence

• Modes of control

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.