Yersinia pestis: Likely Clinical Specimens and Gram Stain Morphology

How to Subscribe
MLS & MLT Comprehensive CE Package
Includes 180 CE courses, most popular
$109Add to cart
Pick Your Courses
Up to 8 CE hours
$55Add to cart
Individual course$25Add to cart
Need multiple seats for your university or lab? Get a quote
The page below is a sample from the LabCE course Preliminary Identification of the Primary Select Agents of Bioterrorism. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

Learn more about Preliminary Identification of the Primary Select Agents of Bioterrorism (online CE course)
Yersinia pestis: Likely Clinical Specimens and Gram Stain Morphology

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

Gram stain of Yersinia pestis bacilli. (6)