a child prsents with infective skin lesions of the leg culture showed hemolytic colonies which were gram +ve cocci in chains.the test to confirm the organism
**Core Concept**
The question is testing the ability to identify a specific bacterium based on its Gram stain appearance, colonial morphology, and hemolytic properties. The bacterium in question is a **Gram-positive coccus** that forms chains and exhibits hemolysis on blood agar.
**Why the Correct Answer is Right**
Given the description of Gram-positive cocci in chains with hemolytic activity, the organism is likely **Streptococcus pyogenes** or another beta-hemolytic streptococcus. To confirm the identity of the organism, a test such as the **bacitracin sensitivity test** or **pyrrolidonyl arylamidase (PYR) test** could be used, as these are commonly used to differentiate among streptococcal species.
**Why Each Wrong Option is Incorrect**
**Option A:** Without knowing the specific test mentioned in Option A, we cannot directly address why it is incorrect, but if it's not related to identifying streptococci, it would be an inappropriate choice.
**Option B:** Similarly, without the details of Option B, we can't comment on its accuracy, but any test not specific for streptococcal identification would be incorrect.
**Option C:** Again, lacking the specifics of Option C, if it doesn't pertain to confirming **Streptococcus** species, it would not be the correct answer.
**Option D:** If Option D does not involve a test for confirming the identity of a streptococcal species, such as those mentioned, it would be an incorrect choice.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that **Streptococcus pyogenes** (Group A streptococcus) is a common cause of skin infections and can be identified by its beta-hemolytic activity on blood agar and its susceptibility to bacitracin.
**Correct Answer:** D. Bacitracin sensitivity test