Public Health & Environmental Laboratories

Safety:

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

Key Characteristics

• Gram-negative bacillus
• Grows at 35-37C, faster at room temperature.
• Catalase positive
• Non-motile (37C and room temperature). Note: Y. pestis is the only species of Yersinia that is non-motile at room temperature.
• Oxidase negative
• Biochemical characteristics: Included in the database of most enteric identification systems, but an identification of Y. pestis must be considered presumptive until confirmed by a reference laboratory.

Colony Characteristics:

• Grows well on most non-selective standard laboratory media (ie. sheep blood, chocolate and tryptic soy agars). Pinpoint, gray-white, non-hemolytic at 24 hrs, by 48 hrs, colonies resemble typical enteric bacteria. After 48-72 hrs, gray-white to slightly yellow opague raised, irregular ““fried egg” appearance; alternatively colonies may have a “hammered copper” shiny surface.
• Grows more slowly than other Enterobacteriaceae at 35-37C, but faster than most at room temperature.
• Grows on MacConkey agar appearing as small non-lactose-fermenting colonies.
• In BHI or other enriched broth, undisturbed growth is flocculent, producing structures resembling stalactites and clumps at the side and bottom of tubes.

Microscopic Characteristics:

• A plump, Gram-negative rod (1.0-2.0 x 0.5 µm).
• Bipolar staining with Wayson or Wright-Giemsa stain and may occasionally be seen in Gram-stained preparations, more common in specimen material than from culture. Note: Although characteristic of Y. pestis, bipolar staining is not always observable and is not unique for Y. pestis.

Resource

• B-Safe Card
• CDC Plague Information