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Bacteriology and Mycology > Francisella > Flashcards

Francisella Flashcards

1
Q

What is the habitat of Francisella tularensis?

A
  • Infected rodents and wild rabbits
  • Various wild animals
  • Occasionally in domestic animals
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2
Q

How is Francisella tularensis transmitted?

A
  • Highest in early winter
    • rabbit hunting
  • Highest during summer
    • ticks and deerflies abundant
  • Direct contact
    • handling infected carcasses
  • Indirect:
    • mosquitos, lice, fleas, tabanids, ticks
  • Contaminated water
  • Under-cooked rabbit meat
  • Inhalation
  • Tick fecal droplets
  • Possibly penetrates skin
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3
Q

How important is the tick to the transmission of Francisella tularensis?

A
  • transmitted transovarily in female ticks
  • They are infective throughout their lifetime
    • 2 years
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4
Q

How many species have been infected with Francisella tularensis?

A
  • Recovered from > 100 animal species
  • Recovered from >54 arthropod species
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5
Q

What is the distribution of Francisella tularensis?

A
  • World wide
  • Seen in KS - VDL
  • Discovered in Tulare County, CA in 1912
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6
Q

What is the colony morphology of Francisella tularensis?

A
  • Small, dew droplet-like
  • Gray (due to hemoglobin uptake) with slight greening around colonies on cystine glucose blood agar
  • Grows well on chocolate agar
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7
Q

What are the characteristics of Francisella tularensis?

A
  • Gram negative
  • very small
  • Aerobe
    • increased CO2 promotes growth, especially on primary isolation
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8
Q

What are the Antigenic Characteristics of Francisella tularensis?

A
  • Capsule is neither immunogenic nor toxic
  • 2 toxic components:
    • 1 stable at 4C - endotoxin
    • 1 labile at 4C - antigenic
  • Facultative intracellular parasite
    • Cell mediate immune response - Type IV hypersensitivity is most protective
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9
Q

What is the resistance of Francisella tularensis?

A
  • Susceptible to commonly used disinfectants
    • 20% commercial bleach (1% sodium hypochloride)
    • 70% ethanol
    • gluteraldehyde, formaldehyde
  • Can survive for 3-6 months in mud, water, or infected carcasses
    • bedbugs - 136 days
    • rabbit meat - 31 days
    • Straw - 192 days
    • grain dust
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10
Q

What is the susceptibility of Francisella tularensis?

A
  • Aminoglycosides
    • Streptomycin, Gentamicin or Kanamycin
  • Tetracyclines and Chloramphenicol also have been used
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11
Q

What are the differential characteristics of Francisella tularensis?

A
  • Grows only on glucose cystine blood agar NOT on plain blood agar
  • Typical tiny dew drop-like gray colonies
  • Fluorescent antibody test
  • Agglutination test for antigen detection
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12
Q

What are the mechanisms of pathogenicity of Francisella tularensis?

A
  • Endotoxin
  • Capsule
  • Virulence genes
    • Macrophage growth locus (2 genes) and Francisella pathogenicity island (19 genes)
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13
Q

What diseases does Francisella tularensis cause?

A
  • Tularemia
  • Deer fly fever
  • Rabbit fever
  • O’Hara’s disease
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14
Q

What animals are affected by Francisella tularensis?

A
  • Humans
  • Rodents
  • Cats
  • Dogs
  • Sheep
  • Game birds
  • Domestic fowl
  • Rare - Horses, swine, cattle
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15
Q

What are the symptoms of a Francisella tularensis infection?

A
  • High temp 104-107F
  • Incubation period 3-5 days
  • Stiffness
  • Weakness
  • Increased respiration
  • Coughing
  • Diarrhea
  • Small necrotic foci
    • liver
    • spleen
    • lymph nodes
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16
Q

What are the different forms of a Francisella tularensis infection?

A
  • Ulcero-Glandular
  • Oculo-Glandular
  • Glandular
  • Penumonic
  • Typohid form
  • Oropharyngeal
  • Intestinal
  • Other forms - rare
17
Q

What is the Ulcero-Glandular form of Francisella tularensis infection?

A
  • Most Common
  • Papule develop at site of infection
    • proceed to ulcers
    • Drain to regional lymph nodes
    • Ln become enlarged and may abscess
  • Difficult to differentiate from Bubonic Plague clinically
18
Q

What is the Oculo-Glandular form of Francisella tularensis infection?

A
  • Similar to Ulcero-glandular form
  • Infection first seen in the eye
19
Q

What is the Glandular form of a Francisella tularensis infection?

A
  • lymph node infection without ulceration
20
Q

What is the Typhoid form of Francisella tularensis infection?

A
  • Systemic infection
  • usually follows other forms
  • Very serious
21
Q

What is the Oropharyngeal form of Francisella tularensis infection?

A
  • Lesions in the pharynx
22
Q

What is the Intestinal form of Francisella tularensis infection?

A
  • Vomiting
  • Diarrhea
23
Q

What is the nature of a Francisella tularensis infection?

A
  • Suppurative
  • Necrotic
  • Granulomatous
24
Q

What is the morbidity / mortality of Francisella tularensis?

A
  • ~150-20 human cases a year
  • Mortality 5-30% untreated cases in N. America
  • Mortality 1% in Europe and Asia
25
Q

How is Francisella tularensis infection diagnosed?

A
  • Agglutination test
  • ELISA
  • Culture
  • Necropsy
26
Q

What is the public health significance of Francisella tularensis ?

A
  • Very significant
  • More reported cases in the human than in animals
  • 10-15 organisms sub-cutaneously or inhaled will cause infection
  • Dose related incubation time 2 - 10 days
  • Not transmitted person-to-person
  • Flies infective for 2weeks
  • Ticks infective for 2 years
  • 15% of vets are positive for F. tularensis antibody in endemic areas
27
Q

What are control measures for Francisella tularensis?

A
  • Vaccinate high risk humans
    • attenuated strain of F. tularensis type B
    • Not licensed by regulatory agencies
  • Bacterins
  • Dry heat 160-170C for 1 hour
  • 20% commercial bleach
  • 70% ethanol
  • Formaldehyde
28
Q

How is Francisella tularensis infection treated?

A
  • Streptomycin
  • Gentamycin
  • Cipro
  • Doxy
  • 7-14 days
29
Q

What is the Growth media for Francisella tularensis?

A
  • Grows on cystine blood agar
  • Does not grow on plain blood agar, atypical stains grow on blood agar
  • DO NOT attempt to culture in laboratory
    • organism is highly invasive and many human infections have been contracted in the lab
30
Q

What are the different species of Francisella tularensis?

A
  • F. tularensis spp. tularensis
    • PFGE Type A I and A II
    • A I is more virulent that A II
      • found in North America
  • F. tularensis spp. holarctica
    • PFGE Type B
      • found in Europe nd Asia
      • Less Virulent
  • F. tuarensis spp. mediaasiatica
  • F. novicida - non-pathogen

Bacteriology and Mycology (35 decks)

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