Which organism is known for causing pneumonic plague?

Yersinia pestis is the organism responsible for pneumonic plague, a severe lung infection that can result from infection with the bacterium. This pathogen is well-known for its role in historical plague outbreaks, including the Black Death. Pneumonic plague occurs when the bacteria infect the lungs, either through inhalation of respiratory droplets from an infected person or by having a primary bubonic plague that then spreads to the lungs.

In the case of Yersinia pestis, it possesses several virulence factors, such as its ability to evade the host's immune response and its rapid replication. This allows for the potential to spread quickly among individuals in close quarters, contributing to its status as a dangerous infectious agent.

The other organisms listed are associated with different diseases. Salmonella enteritidis is primarily linked to foodborne illness and gastroenteritis, Klebsiella pneumoniae is commonly involved in lung infections and other nosocomial infections, and E. coli O157:H7 is well-known for causing severe gastrointestinal illness. Therefore, none of these options directly relate to pneumonic plague, underscoring why Yersinia pestis is the correct choice for this question.