## **Core Concept**
The El Tor biotype of *Vibrio cholerae* is a distinct strain of the bacterium that causes cholera. This biotype is known for its differences in biochemical and biological properties compared to the classical biotype. Understanding the origins and characteristics of different *Vibrio cholerae* biotypes is crucial for epidemiological studies and managing cholera outbreaks.

## **Why the Correct Answer is Right**
The El Tor biotype of *Vibrio cholerae* was first isolated from the El Tor pilgrimage site in Saudi Arabia in 1961. This biotype was initially identified as a cause of cholera among pilgrims. The El Tor biotype is characterized by its ability to cause mild or asymptomatic infections, which contrasts with the classical biotype that typically causes more severe disease. The identification of the El Tor biotype marked a significant shift in the epidemiology of cholera, as it was associated with a pandemic that spread globally.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because there is no widely recognized reference to the El Tor biotype being isolated from this location.
- **Option B:** Similarly, this option does not correspond with historical or scientific records related to the isolation of the El Tor biotype.
- **Option C:** This option is incorrect as it does not align with the documented history of the El Tor biotype's discovery.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the El Tor biotype of *Vibrio cholerae* often causes milder disease and can lead to asymptomatic carrier states, which complicates control and eradication efforts. This biotype's emergence marked a significant change in cholera epidemiology, highlighting the need for ongoing surveillance and adaptation of public health strategies.

## **Correct Answer:** .