Yersinia pestis :: Biology Biological Health Medical Essays

Yersinia pestisLife HistoryYersinia pestis is the causative agent of the general invasive infectious disease often referred to as the plague. The Y. pestis is an extremely sharp pathogen that is likely to cause severe illness and death upon infection unless antibiotics ar administered. In the past, Y. pestis has caused devastating epidemics during three periods of modern history the Justinian Plague spread head from the Middle East to the Mediterranean during the 6th-8th centuries AD and killed approximately 25% of the population below the Alps region. Perhaps the most famous incidence of all disease was the devastating Black Plague of 8th-14th century Europe that eradicated 25 million people (nearly 25% of the population) and marked the end of the Dark Ages. The tertiary endemic began in 1855 in China and was responsible for millions of deaths. Microbiological CharacteristicsYersinia pestis is a Gram-negative, bipolar-staining coccobacillus appendage of the Enterobacteriaceae family, and is an obligate intracellular pathogen that must be contained within the argument to survive. It is also a fermentative, motile organism that produces a thick anti-phagocytic dirty layer in its path. TransmissionY. pestis has the ability to cause disease in gnawers, insects and humans. The primary carriers of the pathogen are the Oriental rat flea, Xenopsylla cheopis, and infected rodents. The path of transmitting to humans usually involves a flea feeding on an infected rodent and becoming a carrier of infection. Once internalized, the bacteria will carry on to reproduce until a large blockage is formed in the midgut of the flea, causing digestion and other gastrointestinal functions to cease. When the flea attempts to feed on humans, the blockage inhibits any linage from entering the stomach cavity instead, portions of the blockage, often containing 11,000-24,000 bacilli, are regurgitated into the mammalian swarm. causticity FactorsYersinia pestis encodes two a ntigenic molecules Fraction 1 (F1) capsular antigen, and VW antigen. Both of these molecules are needed for pathogenicity, and are not expressed at temperatures lower than 37C. This requirement is the main reason why Yersinia is not virulent in fleas, since their body temperature normally levels around 25C. Yersinia is a model for canvas Type III Secretion Systems (TTSS) that inject bacterial proteins into a host cell. In Y. pestis, it is the translocation of Yersinia outer proteins (Yops) that blocks the host cells ability to intercommunicate with immune system cells and down-regulates the response of phagocytic host cells to infection.