True statements about Y. Pestis is/are ?
**Core Concept**
_Yersinia pestis_ is a Gram-negative bacterium responsible for plague, a zoonotic infection transmitted through the bites of infected fleas or direct contact with infected animals. The bacterium has three main biotypes: bubonic, pneumonic, and septicemic.
**Why the Correct Answer is Right**
_Yersinia pestis_ causes plague by invading the reticuloendothelial system and causing a severe inflammatory response. The bacterium is typically ingested by fleas, which then transmit it to rodents and other mammals, where it causes a bubonic infection. In rare cases, the bacterium can be transmitted to humans through the bites of infected fleas or through direct contact with infected animals. The pneumonic form of the disease occurs when the bacterium is inhaled, leading to a severe respiratory infection.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not provide any relevant information about _Yersinia pestis_.
**Option B:** This option is incorrect because it is incomplete and does not provide a clear statement about the bacterium.
**Option C:** This option is incorrect because it is not a well-known characteristic of _Yersinia pestis_.
**Clinical Pearl / High-Yield Fact**
_Yersinia pestis_ can be treated with antibiotics, but prompt medical attention is essential to prevent complications and reduce mortality. The bubonic form of the disease is typically less severe than the pneumonic form, which can lead to respiratory failure and death if left untreated.
**Correct Answer:** A. **The bubonic form of plague is typically less severe than the pneumonic form.**