Master Yersinia Pestis (Black Plague) with Picmonic for Medicine

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Yersinia pestis is a gram negative coccobacillus that can cause pneumonia, septicemia, and the bubonic plague. This organism is widely believed to be responsible for the death of approximately one third of the European population between 1347 and 1353. Today, the reservoir for this organism is several species of rodents including the black-tailed prairie dog, commonly found in the Southwest region, and transmitted via the flea vector. There have been several incidents of human transmission in people exposed to these animals. Pathogenesis includes several factors that allow the bacteria to suppress and avoid the normal immune response including an anti-phagocytic polysaccharide capsule and anti-phagocytic F1 and VW antigens that inhibit macrophages. Yersinia pestis is known to proliferate inside lymph nodes, causing lymphadenopathy and buboes, most frequently involving the inguinal lymph nodes. The term buboes gave rise to the name the bubonic plague. The organism could also get into the lungs causing a severe pneumonia with symptoms of chest pain, dyspnea, and hemoptysis. If the organism gets into the bloodstream, it can cause septicemic plague with complications of disseminated intravascular coagulation (DIC). Widespread DIC causes destruction of the blood vessels and results in black cutaneous hemorrhagic lesions on the skin. Many historians believe these lesions gave rise to the name “Black Death.”

16 KEY FACTS

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

These bacteria are small and sometimes described as resembling coccobacilli, but they are actually 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 lactose nonfermenter because it cannot utilize lactose sugars in culture. The bacteria grows as white or colorless colonies on MacConkey agar, which is used to test for lactose fermenting capability.

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

Today, the reservoir for this organism is several species of rodents. This includes the black-tailed prairie dog, commonly found in the Southwest region, and transmitted via the flea vector.

Yersinia pestis has a polysaccharide capsule as a virulence factor, which aids in evading phagocytosis.

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 rodents that act as a reservoir for this organism are commonly found in the Southwest region of the United States.

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

In the lungs, Yersinia pestis can cause a severe pneumonia, with symptoms of chest pain, dyspnea, and hemoptysis.

If the organism gets into the bloodstream, it can cause septicemic plague with complications of disseminated intravascular coagulation (DIC). Widespread DIC causes destruction of the blood vessels, and results in black cutaneous hemorrhagic lesions on the skin. Many historians believe these lesions gave rise to the name “Black Death.”

Yersinia pestis is known to proliferate inside lymph nodes, causing lymphadenopathy and buboes, most frequently involving the inguinal lymph nodes. 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.

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