Master Yersinia Pestis (Black Plague) with Picmonic for Medicine

This organism stains Gram-negative due to the relatively thin peptidoglycan layer in the cell wall.

These bacteria are small and can present as coccobacilli but are actually classified as rods.

The oxidase test is used to determine if a bacterium produces certain cytochrome c-oxidases in order to use oxygen for energy production. Yersinia pestis is oxidase-negative meaning it does not use the electron transport chain to make energy.

Yersinia pestis is characterized as a non-lactose fermenter because it cannot utilize lactose sugars in a culture. The bacteria grows as white or colorless colonies on MacConkey agar, a medium used to test for lactose fermenting capability.

Today, the reservoir for this organism is several species of rodents including the black-tailed prairie dog.

Yersinia Pestis-infected fleas residing on species of rodents and other mammals and can transmit the bacterium through their saliva/emesis into the host.

Yersinia pestis has a polysaccharide capsule as a virulence factor, aiding in evasion of phagocytosis by macrophages and others.

Vw antigen is an antiphagocytic virulence mechanism that aids in the pathogenesis of Yersinia pestis.

F1 antigen is an antiphagocytic virulence mechanism that aids in the pathogenesis of Yersinia pestis.

This bacterium has several antiphagocytic mechanisms, including a polysaccharide capsule, F1 antigen, and Vw antigen that inhibit phagocytosis by macrophages.

The arid climate and environment of the American Southwest harbor the rodents typical of carrying fleas infected by Yersinia Pestis.

Yersinia pestis is known to proliferate inside lymph nodes, causing lymphadenopathy.

Yersinia pestis can lead to the development of pneumonia when infecting the respiratory tract/pulmonary system.

In the case of septicemia (e.g. a blood infection), a further complication includes disseminated intravascular coagulation (DIC). Widespread DIC causes destruction of the blood vessels and result in developing black cutaneous hemorrhagic lesions of the skin. Many historians believe these lesions gave rise to the name “Black Death.”

Yersinia pestis is known to proliferate inside lymph nodes, resulting in the development of lymphadenopathy and buboes. A common region of developing lymphadenopathy and buboes is the inguinal region. The term buboes gave rise to the name the "bubonic" plague.

When tested with giemsa staining,Yersinia pestis has a bipolar staining pattern. This is due to the ends of the bacterium taking up more stain than the center of the organism.