Lepra bacilli can survive outside the human body up to:
**Core Concept**
Lepra bacilli, also known as Mycobacterium leprae, are acid-fast bacilli that cause leprosy. Their ability to survive outside the human body is influenced by temperature, pH, and nutrient availability.
**Why the Correct Answer is Right**
Lepra bacilli can survive outside the human body for up to 5 days in a moist environment, but they are sensitive to temperature extremes and desiccation. They can maintain viability at temperatures between 20°C to 30°C, which is within the range of human body temperature. However, they are rapidly killed by temperatures above 40°C or below 15°C.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because lepra bacilli do not survive for an extended period outside the human body. While they can persist for a short time, they are not as resilient as other mycobacteria like M. tuberculosis.
**Option B:** This option is incorrect because there is no evidence to suggest that lepra bacilli can survive for more than 5 days outside the human body.
**Option C:** This option is incorrect because lepra bacilli are not as heat-resistant as some other bacteria, and they are rapidly killed by temperatures above 40°C or below 15°C.
**Clinical Pearl / High-Yield Fact**
It's essential to note that lepra bacilli are obligate parasites, meaning they require a living host to survive. This characteristic makes them difficult to culture in the laboratory, and diagnosis often relies on clinical evaluation and biopsy.
**Correct Answer: C. 5 days.**