Which bacterial agent is responsible for causing the bubonic, pneumonic, and septicemic forms of the plague?

Correct option is C

Sol. Yersinia pestis is the bacterial agent responsible for causing plague, which manifests in three forms: bubonic, pneumonic, and septicemic plague. This Gram-negative, rod-shaped bacterium is transmitted primarily through the bite of infected fleas, often found on rodents. Bubonic plague affects the lymph nodes, pneumonic plague affects the lungs and can be airborne, and septicemic plague occurs when the bacteria spread through the bloodstream, leading to severe complications.
Explanation of each option:
· (a) Francisella tularensis – Incorrect. Francisella tularensis causes tularemia, also known as rabbit fever, and is not responsible for plague.
· (b) Rickettsia rickettsii – Incorrect. Rickettsia rickettsii causes Rocky Mountain spotted fever (RMSF), a tick-borne disease, not plague.
· (c) Yersinia pestis – Correct answer. This bacterium is the causative agent of plague, responsible for outbreaks such as the Black Death in the 14th century.
· (d) Bacillus anthracis – Incorrect. Bacillus anthracis causes anthrax, a disease that affects livestock and humans through spores, not flea transmission.