Compare and contrast Yersinia pestis and Francisella tularensis with respect to clinical manifestations, mechanisms of transmission, reservoirs, and pathogenesis.

Question

What will be an ideal response?

Answer 1

Yersinia pestis causes bubonic plague, characterized by enlarged, necrotic lymph nodes and high fever, often progressing to bacteremia and DIC. Francisella tularensis cause tularemia which causes fever, headache and muscle aches, sore throat and nausea. Both organisms can produce a pulmonary form of disease if the bacterium travels via the blood or aerosol to the respiratory tract. Yersinia can also be transmitted to the respiratory tract person to person if it is pneumonic while Francisella cannot. Francisella can establish an infection from skin contact and cause a skin ulcer at the site of the site of infection. Yersinia does not infect the skin.

Both organisms can be transmitted by an arthropod vector. For Y. pestis, the vector is usually a flea, whereas for F. tularensis, vectors can be flies, mosquitoes, mites, or ticks. Francisella can also be transmitted by contact with contaminated animals, by ingesting contaminated animals or water, or by inhaling aerosols. Yersinia can be transmitted by contact with an infected animal. Francisella has many hosts; rabbits, ticks, and muskrats are the most common reservoirs. Rodents are the most common reservoirs for Yersinia. 

Yersinia is pathogenic by injecting deadly proteins into cells triggering apoptosis, whereas Francisella is an intracellular parasite that inhibits phagocytosis by an unknown mechanism.