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Doneen Hollingsworth, Secretary of Health

Francisella tularensis — Key Characteristics

F. tularensis is highly infectious! Once this organism is suspected on the basis of clinical and/or laboratory information, do not perform additional testing. Send the isolate to the South Dakota State Laboratory for identification.

  • Gram-negative, tiny pleomorphic, poorly staining, coccobacillus.
  • Sheep blood agar – grows poorly with very tiny colonies.
  • Chocolate agar (cystine enriched) – grows slowly.
  • Oxidase negative.
  • Nonmotile.
  • Urease negative.
  • Beta-lactamase positive.
  • X and V factors are not required.

Pitfalls

  • Not in the database of most commercial systems.
  • Caution: This organism looks like Haemophilus, but do not smell it. F. tularensis has been reported to cross intact skin. Leave lids on plates.

Look-a-likes

  • H. influenzae
  • Acinetobacter
  • Actinobacillus
  • H. aphrophilus
  • Pasturella
  • Bordetella
  • Group IV
  • Capnocytophaga
  • Kingella
  • Legionella
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