Yersinia Pestis And The Plague

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Yersinia pestis and the Plague
Jin You
MMI 133
Dr. Judith Gnarpe

One organism that commonly causes diseases in humans is Yersinia pestis. This bacterium is the causative agent of the infamous bubonic plague, primary septicaemic plague, and primary pneumonic plague. Y. pestis was first discovered by Shibasaburo Kitasato and Alexandre Yersin, but due to Yersin’s description of the bacteria being more accurate, this bacterium was named after him (3). There are still disputes going on for who had correctly identified Y. pestis first. Yersinia pestis belongs to the Enterobacteriaceae bacteria family and is a Gram-negative coccobacillus. It is non-motile, non-spore forming, a facultative anaerobic bacillus that displays bipolar staining with
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The bacteria have a coagulase that forms a blood clot in the flea, which inhibits them from swallowing. The Y. pestis then multiplies in the blood of the flea. When the flea bites a human, it regurgitates a mass amount of bacteria into the skin, where it migrates to the lymph nodes (via cutaneous lymphatic system). In naturally occurring cases of the plague, transmission is through the bite of infected fleas. In cases of primary pneumonic plague, the disease may be contracted after exposure to a patient who is sick with the plague and also has a cough by droplet transmission (2). The primary pneumonic plague, although it is the most lethal type of the plague, is also the most rare type of the infection. Y. pestis has multiple virulence factors which is activated upon entering into the mammalian host (resulting in a change of temperature from lower temperature to around 37°C). For invasion, it has a protease called the plasminogen activator (Pla) that breaks down fibrin. This allows it to spread systemically from the original inoculation site (area of flea bite). This bacterium also has a hemin storage system, which enables it to survive in phagocytic cells and enhances uptake into eukaryotic (host’s) cells. Y. pestis also encode a type 3 secretion system (T3SS), which is a secretion system made up of macromolecular structures that lines the inner and outer membranes of the bacteria. It enables the direct translocation, from bacterial cytosol into host cells, of
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