Listeria

• What is the species of Listeria that is an important cause of disease in humans and animals?

  Listeria monocytogenes

  
• What distinguishes Listeria monocytogenes from other bacteria like corynebacteria?

  It exhibits tumbling motility at room temperature but not at 37ºC
• What type of bacteria is Listeria monocytogenes in terms of gram staining?

  Gram positive

  
• What type of anaerobes are Listeria monocytogenes?

  Catalase positive facultative anaerobes
• What are the two types of listeriosis disease?

  • Perinatal:
  • Early onset: intrauterine infection, sepsis, and death before birth
  • Late onset: infection at birth, meningitis, and sepsis within 2-3 weeks
  • Adult:
  • Flu-like symptoms and gastro upset in immunocompetent individuals
  • Meningo-encephalitis and bacteraemia in immunocompromised individuals
• How much more susceptible are pregnant women to listeriosis compared to non-pregnant individuals?

  20% more susceptible
• What is the main reservoir of infection for Listeria monocytogenes?

  Infected animals, environment, silage, and infected humans
• What is the normal route of infection for Listeria monocytogenes?

  Gastrointestinal route
• What foods are commonly associated with Listeria infection and outbreaks?

  • Soft unpasteurized cheeses
  • Packaged meats like luncheon meat
  • Fruits and vegetables
• How can Listeria infection be avoided?

  By pasteurizing dairy and cooking food
• What characteristic allows Listeria monocytogenes to grow in cold temperatures?

  It is psychotropic
• Describe the pathogenesis of Listeria monocytogenes.

  • Intracellular bacteria that grow inside cells (macrophages)
  • Taken up to phagosome
  • Produces enzyme to lyse phagosome
  • Forms F actin tail to push itself into other cells

  
• What type of organisms are Streptomyces?

  Abundant soil organisms
• What is the structure of Streptomyces?

  Mycelial
• What do Streptomyces generate at the ends of terminal hyphae?

  Spores
• What type of bacteria are Streptomyces in terms of oxygen requirement?

  Strict aerobes
• What is significant about the nutritional versatility of Streptomyces?

  • They can grow in various environments
  • They produce many antibiotics
• What is the effect of Streptomyces antibiotics on other bacteria?

  They prevent the growth of other bacteria on the plate

  
• What is the general shape of Corynebacteria?

  Club-shaped rods
• What does the term "Koryne" in Greek refer to in relation to Corynebacteria?

  It means club
• What are the types of Corynebacteria?

  • Animal pathogens
  • Plant pathogens
  • Saprophytes
• What is the specific species of Corynebacteria that causes diphtheria?

  Corynebacterium diphtheriae
• What are the characteristics of diphtheria as described by the CDC?

  • Upper respiratory tract illness
  • Characterized by sore throat, low-grade fever
  • Adherent membrane of the tonsils, pharynx, and/or nose
• How does diphtheria spread?

  By droplets or contact
• What do toxigenic strains of Corynebacterium diphtheriae produce?

  A toxin
• What is the effect of the diphtheria toxin on the body?

  • Absorbed onto the mucous membrane
  • Causes destruction of epithelium
  • Produces local inflammation
  • Forms a greyish "pseudomembrane"
• What are the severe symptoms of diphtheria attributed to?

  The action of the toxin transported in the blood
• What are the potential lesions caused by diphtheria toxin?

  • Kidney lesions
  • Heart lesions
  • Nervous system lesions
  • Acute nephritis
  • Serious weakness of the heart
  • Paralysis
• What is the mortality rate of diphtheria even with treatment?

  1. 10%
• How many children die each year from diphtheria?

  4000 children
• What encodes the diphtheria toxin?

  A lysogenic phage
• What are the two domains of the diphtheria toxin and their functions?

  • Domain A: Catalytic domain, prevents protein synthesis
  • Domain B: Receptor-binding domain, binds to cell surface

  
• What is the lethal dose of diphtheria toxin for humans?

  About 0.1 µg/kg
• What is used as a vaccine for diphtheria?

  Inactivated toxoid
• What is used for the treatment of diphtheria?

  Antitoxin and antibiotics (e.g., erythromycin)
• What is the Elek test used for?

  • To test for the toxigenicity of Corynebacterium diphtheriae
  • Involves antitoxin soaked filter paper and perpendicular streaked samples