DCA media used in differentiation of which infection?
**Core Concept**
The question is testing the student's knowledge on the differentiation of bacterial infections using special media. DCA (Dextrose Colloidal Agar) media is a type of selective medium used in clinical microbiology to differentiate between certain bacterial infections.
**Why the Correct Answer is Right**
DCA media is specifically used to differentiate between **Haemophilus influenzae** and **Neisseria gonorrhoeae**. The key to this differentiation lies in the ability of H. influenzae to ferment glucose in the presence of dextrose, whereas N. gonorrhoeae does not. This property allows for the selective growth of H. influenzae on DCA media, making it a useful tool in the laboratory diagnosis of these infections.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because DCA media is not used for the differentiation of Staphylococcus aureus and Streptococcus pyogenes.
* **Option B:** This option is incorrect because DCA media is not used for the differentiation of Escherichia coli and Klebsiella pneumoniae.
* **Option C:** This option is incorrect because DCA media is not used for the differentiation of Pseudomonas aeruginosa and Acinetobacter baumannii.
**Clinical Pearl / High-Yield Fact**
When using DCA media for the differentiation of H. influenzae and N. gonorrhoeae, it's essential to note that the presence of catalase-positive bacteria can lead to false-negative results. This is because catalase can break down the dextrose in the medium, preventing the growth of H. influenzae.
**Correct Answer:** D. DCA media is used in the differentiation of Haemophilus influenzae and Neisseria gonorrhoeae.