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Yersinia pastis is a strain of bacteria linked to the Black Death and still active today, primarily in small animal reservoirs. It can cause bubonic, septicemic, and pneumonic plague in humans, but is treatable with antibiotics, although some strains are developing resistance. Major outbreaks are rare, but the microbe infects 1,000 to 2,000 people a year and kills about one in seven.
Yersinia pastis is an alternative spelling of Yersinia pestis and refers to a strain of bacteria. This bacterium has been linked to the Black Death and remains active in the modern world, although it is generally confined to a small number of animal reservoirs. Yersinia pastis is anaerobic and gram negative. Infection with this microbe, while very serious, can be successfully treated with modern antibiotic drugs, although some strains appear to develop antibiotic resistance.
This microbe was first identified and linked to the plague in the late 19th century, a link that has since been conclusively proven with the help of DNA testing. The discovery of Yersinia pastis has allowed researchers to piece together a comprehensive understanding of the typical Black Death cycle of diseases. The bacterium is normally carried by a small mammalian host species, typically rats, marmots or similar animals. The fleas then transfer the microbe to human hosts. Human-to-human transmission of the plague is also possible, but is generally a form of secondary transmission.
Three forms of Yersinia pastis infection are generally seen in humans. The most common variety of infection, transmitted directly by flea bites, leads to bubonic plague, the most common form of plague, which produces painful swelling in the lymph nodes and many general systemic symptoms. Septicemic plague occurs when the microbe is able to directly infect the bloodstream and is a very dangerous form of the disease, especially if left untreated. Pneumonic plague is an infection of the lungs and an extremely serious one, not least because it produces a devastating cough that allows the microbe to infect new hosts via airborne transmission.
Yersinia pastis is endemic to many regions of the globe, including Southeast Asia and the American Southwest. Major outbreaks of plague are rare in the modern world, and none have occurred in the United States since the 1920s. This microbe, however, remains a threat, infecting 1,000 to 2,000 people a year and killing about one in seven.
Antibiotics are currently very effective at treating Yersinia pastis infection, but recent research suggests that resistance may be on the rise. Bacteria are often able to exchange DNA elements with each other in nature, and Yersinia pastis appears to have been able to acquire antibiotic resistance-producing genes through exchange with other, much more common bacteria. These bacteria have developed drug resistance in response to the widespread use, frequent overuse, and abuse of antibiotics.
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