Yersinia pestis: Culture Characteristics, Colony Morphology, and Hallmark Features

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Yersinia pestis: Culture Characteristics, Colony Morphology, and Hallmark Features

Culture Characteristics:
  • Growth at 22-25oC and at 35oC
  • Organism prefers 25oC, so the colonies will grow faster at this temperature
  • Growth occurs on most routine media, including sheep blood agar (SBA), chocolate agar (CHOC), MacConkey (MAC) agar, and routine blood culture media
  • Non-lactose fermenter on MAC agar
  • Growth is slower than other Enterobacteriaceae
Colony Morphology on SBA at 35oC:
  • At 24 hours, colonies are pinpoint and translucent with a gray-white color
  • Colonies take on a yellow tint as they age, after 48-72 hours, referred to as a "hammered copper" appearance
  • An irregular or "fried egg" appearance, shown in the lower image, can also be seen at 48-72 hours
Characteristic Features:
  • Growth at 22-25oC is a hallmark feature of this organism
7. CDC/Dr. Brodsky. Image #3361. "This image depicts a front view of a Petri dish culture plate, which had contained a growth medium of blood agar, that had been inoculated with Yersinia pestis bacteria, and is seen here after a 48-hour inoculation period." PHIL, 1966 public domain. Accessed May 25, 2022. https://phil.cdc.gov/Details.aspx?pid=3361
8. CDC/L Stauffer. Image #1921. "This petri dish culture plate contained a growth medium of sheep blood agar (SBA), which had been inoculated with Yersinia pestis and incubated for a 72-hour period. Note the classic fried egg colonial morphology produced by Y. pestis." PHIL, 2002, public domain. Accessed May 25, 2022.
https://phil.cdc.gov/Details.aspx?pid=1921

Blood agar inoculated with Yersinia pestis
after 48 hours of incubation. (7)
Sheep blood agar (SBA) with Yersinia pestis after
72 hours of incubation. Note the classic fried egg
colonial morphology produced. (8)