Francisella tularensis

Categorization
Cell Wall: Gram Negative Shape: Rod
Life Cyle: Facultative Intracellular
Transmission
  • The natural reservoir of F. tularensis is a variety of wild mammals and thus the organism is a zoonotic. Humans can be infected in a number of ways including blood meals by insects which have previously come in contact with infected animals, inhalation of aerosolized droplets, or ingestion of contaminated food and water. F. tularensis infection is most commonly observed in the Southern US.
Virulence Factors
  • F. tularensis possesses a thin anti-phagocytic capsule which allows it to survive, multiply, and be transported within host cells, thus qualifying for facultative intracellular status.
Diagnosis
  • Because direct culture of F. tularensis is difficult, detection of specific antibody to the organism is most commonly used for diagnosis.
Clinical Consequences
  • Overview
    • Depending on the mode of inoculation, several different clinical forms of Tularemia can appear.
  • Ulceroglandular Tularemia
    • Ulceroglandular Tularemia is caused by inoculation of the skin through the bite of an infected insect or during skinning of an infected animal via abrasions. Initially the skin around the inoculation site becomes erythematous and over time evolves into a punched-out ulcer with a necrotic, black base. Concurrently, painful lymphadenopathy of the regional lymph nodes occurs and over time lymph nodes become necrotic and purulent. In a minority of individuals, organisms can gain access to the blood stream and disseminate widely
  • Oculoglandular Tularemia
    • Oculoglandular Tularemia occurs via infection of the conjunctiva through inoculation with contaminated fingers. An ulcerative conjunctivitis develops followed by purulent lymphadenopathy of local lymph nodes.
  • Pulmonary Tularemia
    • Pulmonary Tularemia occurs following inhalation of organisms during skinning of an infected animal. Disease resembles an atypical community-acquired pneumonia and can disseminate widely in the blood stream if not treated.
Treatment
  • Gentamicin, streptomycin, or tetracycline are effective