Microbiology
Summary
The Yersinia genus includes Yersinia enterocolitica and Yersinia pestis. Yersinia bacteria are gram-negative pathogens that exhibit bipolar staining and an encapsulated structure. Y. enterocolitica is transmitted through contaminated food and water, unpasteurized milk, and dog feces. It causes bloody diarrhea, fever, leukocytosis, and abscesses, and can also mimic appendicitis.
On the other hand, Y. pestis is responsible for the infamous Black Death or bubonic plague. It is transmitted to humans through fleas that have bitten infected rodents, primarily prairie dogs in the United States. Infection with Y. pestis is characterized by the appearance of swollen, tender lymph nodes, called buboes. This gram-negative organism can lead to serious diseases such as organ abscesses, DIC, and cutaneous hemorrhage. Y. pestis secretes virulence factors called Yersinia-associated outer proteins (Yops) through a type III secretion system. The recommended treatment for Yersinia infections includes aminoglycosides, such as streptomycin, in combination with tetracycline. There is also a killed vaccine available for Y. pestis prevention, although it is not routinely used or tested.
Lesson Outline
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FAQs
Y. enterocolitica and Y. pestis are both gram-negative, encapsulated, bipolar-staining bacteria, but they cause different disease manifestations and spread through different routes. Y. enterocolitica is primarily associated with gastrointestinal infections, causing symptoms like bloody diarrhea and pseudoappendicitis. In contrast, Y. pestis is the causative agent of the bubonic plague. Y. enterocolitica is usually transmitted through contaminated food and water, as well as dog feces, while Y. pestis spreads through flea bites or contact with infected animals or bodily fluids.
Yersinia bacteria are described as gram-negative because they have a thin peptidoglycan layer within their cell walls and are unable to retain the crystal violet stain in the Gram stain process. The outer membrane of these bacteria contains lipopolysaccharides, which contribute to their pathogenicity. Bipolar staining, also called "safety pin" staining, describes the appearance of Yersinia bacteria when stained with certain dyes. The staining reveals a clear central region with darkly stained poles at both ends of the rod-shaped bacteria, resembling a safety pin.
Y. pestis is the causative agent of the bubonic plague, a deadly infectious disease that has caused several pandemics throughout history. The bubonic plague is transmitted to humans through the bite of infected fleas, which are often found on rodents like rats. Y. pestis infection results in swollen and painful lymph nodes, called buboes, fever, chills, and weakness. The disease has a high fatality rate if left untreated, and it killed millions of people during the Middle Ages.
Infection with Y. enterocolitica causes symptoms such as fever, abdominal pain, and bloody diarrhea. The pain can mimic appendicitis, resulting in a condition known as pseudoappendicitis. The bacteria are usually transmitted through the consumption of contaminated food or water, especially undercooked pork products or unpasteurized milk. Y. enterocolitica can also be transmitted through direct contact with infected animals or their feces (such as dogs).
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