Clinical specimens where organisms 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), a "safety-pin-like" appearance.
Note: Using Wright-Giemsa staining on direct specimens may enhance the demonstration of characteristic bipolar staining, also referred to as "safety-pin" morphology. The use of this staining is of limited value, as the method is not very sensitive or specific.
