Francisella Flashcards
What is the habitat of Francisella tularensis?
- Infected rodents and wild rabbits
- Various wild animals
- Occasionally in domestic animals
How is Francisella tularensis transmitted?
- 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
How important is the tick to the transmission of Francisella tularensis?
- transmitted transovarily in female ticks
- They are infective throughout their lifetime
- 2 years
How many species have been infected with Francisella tularensis?
- Recovered from > 100 animal species
- Recovered from >54 arthropod species
What is the distribution of Francisella tularensis?
- World wide
- Seen in KS - VDL
- Discovered in Tulare County, CA in 1912
What is the colony morphology of Francisella tularensis?
- Small, dew droplet-like
- Gray (due to hemoglobin uptake) with slight greening around colonies on cystine glucose blood agar
- Grows well on chocolate agar
What are the characteristics of Francisella tularensis?
- Gram negative
- very small
- Aerobe
- increased CO2 promotes growth, especially on primary isolation
What are the Antigenic Characteristics of Francisella tularensis?
- 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
What is the resistance of Francisella tularensis?
-
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
What is the susceptibility of Francisella tularensis?
- Aminoglycosides
- Streptomycin, Gentamicin or Kanamycin
- Tetracyclines and Chloramphenicol also have been used
What are the differential characteristics of Francisella tularensis?
- 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
What are the mechanisms of pathogenicity of Francisella tularensis?
- Endotoxin
- Capsule
- Virulence genes
- Macrophage growth locus (2 genes) and Francisella pathogenicity island (19 genes)
What diseases does Francisella tularensis cause?
- Tularemia
- Deer fly fever
- Rabbit fever
- O’Hara’s disease
What animals are affected by Francisella tularensis?
- Humans
- Rodents
- Cats
- Dogs
- Sheep
- Game birds
- Domestic fowl
- Rare - Horses, swine, cattle
What are the symptoms of a Francisella tularensis infection?
- High temp 104-107F
- Incubation period 3-5 days
- Stiffness
- Weakness
- Increased respiration
- Coughing
- Diarrhea
- Small necrotic foci
- liver
- spleen
- lymph nodes
What are the different forms of a Francisella tularensis infection?
- Ulcero-Glandular
- Oculo-Glandular
- Glandular
- Penumonic
- Typohid form
- Oropharyngeal
- Intestinal
- Other forms - rare
What is the Ulcero-Glandular form of Francisella tularensis infection?
- 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
What is the Oculo-Glandular form of Francisella tularensis infection?
- Similar to Ulcero-glandular form
- Infection first seen in the eye
What is the Glandular form of a Francisella tularensis infection?
- lymph node infection without ulceration
What is the Typhoid form of Francisella tularensis infection?
- Systemic infection
- usually follows other forms
- Very serious
What is the Oropharyngeal form of Francisella tularensis infection?
- Lesions in the pharynx
What is the Intestinal form of Francisella tularensis infection?
- Vomiting
- Diarrhea
What is the nature of a Francisella tularensis infection?
- Suppurative
- Necrotic
- Granulomatous
What is the morbidity / mortality of Francisella tularensis?
- ~150-20 human cases a year
- Mortality 5-30% untreated cases in N. America
- Mortality 1% in Europe and Asia
How is Francisella tularensis infection diagnosed?
- Agglutination test
- ELISA
- Culture
- Necropsy
What is the public health significance of Francisella tularensis ?
- 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
What are control measures for Francisella tularensis?
- 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
How is Francisella tularensis infection treated?
- Streptomycin
- Gentamycin
- Cipro
- Doxy
- 7-14 days
What is the Growth media for Francisella tularensis?
- 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
What are the different species of Francisella tularensis?
-
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
- PFGE Type B
- F. tuarensis spp. mediaasiatica
- F. novicida - non-pathogen
