Clinical specimens where organism may be encountered:
- Blood
- Lymph node aspirate
- Respiratory secretions
Gram stain morphology:
- Gram-negative rod, may appear plump and as a coccobacilli
- In the family Yersiniaceae, order Enterobacterales
- Resembles other enteric gram-negative rods
- In single cells or pairs, but can form short chains
- Gram stains performed from blood culture or other liquid media may show bipolar staining (displayed by the arrows); "safety-pin-like" appearance.
Note:Use of Wright-Giemsa staining on direct specimen may enhance demonstration of characteristic bipolar staining, also referred to as "safety-pin" morphology. Use of this staining is of limited value, as the method is not very sensitive or specific.
6. CDC/L. Stauffer. Image #1915. Caption: "This photomicrograph reveals the presence of numerous, rod-shaped, Gram negative, Yersinia pestis bacilli." PHIL 2002, public domain image. Accessed May 25, 2022. https://phil.cdc.gov/Details.aspx?pid=1915
