Public Health & Environmental Laboratories

F. tularensis is highly infectious. Once this organism is suspected on the basis of clinical and/or laboratory information, additional testing MUST be performed within a certified biosafety cabinet.

Safety:

• Biosafety Level 2 for processing clinical specimens.
• Biosafety Level 3 practices for all culture manipulations that might produce aerosols.

Key Characteristics

• Gram-negative, very tiny coccobacillus
• Does not grow on MacConkey or EMB agar
• Grows slowly at 35-37C, on sheep blood, chocolate or Thayer-Martin agar, does not require CO2.
• Catalase negative, or weakly positive
• Non-motile
• Oxidase negative
• Urease negative
• X and V factors are not required.

Colony Characteristics:

• Grows poorly on sheep blood agar: 1-2 mm, gray-white, non-hemolytic at 48-72 hrs.
• On chocolate or Thayer-Martin agar: 1-3 mm, gray-white to bluish-gray with entire border and smooth flat surface at 48-72 hrs. Growth in thioglycollate broth is slow, with denser band near top, diffusing with age.
• Ability to grow on sheep blood agar usually lost on subculture.

Microscopic Characteristics:

Faintly staining, very tiny Gram-negative coccobacillus (0.2-0.7 x 0.7-1.0 µm), seen mostly as single cells. Bipolar staining is not a distinctive feature. Cells are smaller than those of Brucella spp.

Resource

• B-Safe Card
• CDC-Tularemia