Which of the following pleomorphic coccobacillus shows satellite phenomenon in blood agar?
**Core Concept**
The satellite phenomenon in blood agar is a characteristic growth pattern exhibited by certain microorganisms that require an accessory growth factor, which is provided by another bacterium. This is a key diagnostic feature for identifying specific pathogens.
**Why the Correct Answer is Right**
The satellite phenomenon in blood agar is typically associated with Corynebacterium diphtheriae, which requires a nutritional supplement, usually provided by the growth of Staphylococcus aureus or other bacteria. The accessory growth factor, usually a vitamin or a nutrient, is secreted by the other bacterium, allowing the Corynebacterium to grow as a smaller colony around the larger colony of the accessory bacterium. This growth pattern is a distinctive feature of C. diphtheriae.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not exhibit the satellite phenomenon in blood agar. The incorrect option does not provide a clear alternative explanation.
**Option B:** This option is incorrect because it does not match the description of the satellite phenomenon in blood agar. The incorrect option does not provide a clear alternative explanation.
**Option C:** This option is incorrect because it does not demonstrate the characteristic growth pattern of the satellite phenomenon. The incorrect option does not provide a clear alternative explanation.
**Clinical Pearl / High-Yield Fact**
Corynebacterium diphtheriae is a gram-positive rod that exhibits a distinctive "metachromatic" staining pattern due to the presence of granules that contain the enzyme phospholipase C. This enzyme is responsible for the pathogenic effects of the bacterium.
**Correct Answer: C. Corynebacterium diphtheriae**