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Francisella tularensis

Francisella tularensis. First isolated from rodents in 1919 by Dr. Francis (Tulare County, CA) Considered the most virulent organism that infects humans ~200 cases /year, in all 50 states . Epidemiology. Morphology and Physiology. Gram-negative rod, pleomorphic (coccoid to filamentous).

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Francisella tularensis

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  1. Francisella tularensis • First isolated from rodents in 1919 by Dr. Francis (Tulare County, CA) • Considered the most virulent organism that infects humans • ~200 cases /year, in all 50 states

  2. Epidemiology

  3. Morphology and Physiology • Gram-negative rod, pleomorphic (coccoid to filamentous) Facultative anaerobe Requires a rich medium plus cystine to grow

  4. Reservoirs and Transmission • Wild mammals (rabbits, squirrels, muskrats, beavers, deer) • Transmission by tick, deer fly, skin abrasion and transovarial

  5. …..and of the hare “ ......of their flesh shall ye not eat, and their carcass shall ye not touch, they are unclean to you .” (Leviticus XI:6-8)

  6. Infection • Infected insect bite • Contact of abraded skin with infected material

  7. Major Clinical Manifestations • Ulceroglandular (70-85%) • Glandular (5-10%) • Typhoidal (5-10%) • Pneumonic (1-5%) • Oculoglandular (1-2%) • Oropharyngeal (rare)

  8. Ulceroglandular tularemia • Local ulceration • Local lymphadenopathy • Bacteremia and fever • Disseminated lymphadenopathy

  9. Tularemic ulcer Primary lesion (papule) forms at point of entry Becomes an open ulcer in about a week

  10. Pneumonic tularemia • Acquire either via the mechanisms of ulceroglandular or from direct respiratory route from skinning an infected rabbit or from another person with pneumonic tularemia • High mortality

  11. Typhoidal tularemia • Acquired by ingestion of food or water contaminated with high number of organisms due to animals that died from tularemia • Symptoms similar to typhoid fever (GI distress and high fever)

  12. Treatment • Difficult because organisms are intracellular • Long term streptomycin therapy commonly used • Immunity is cell-mediated, so killed vaccines of little value • Attenuated strain vaccine available for high risk person

  13. Prevention • Wear rubber gloves when in contact infected material • Watch out for ticks

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