This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Systemic Bacteriology (Gram Positive Cocci, Gram Negative Cocci), Subject name: Microbiology
Which of the following is catalase positive? 
Select and explain. 
A. Staph epidermidis, B. Enterococcus, C. Streptococcus, D. Pneumococcus
A: Staph epidermidis
Answer: A: Staph epidermidis 
Explanation: Catalase test is used mainly to differentiate between Staphylococcus(Catalase positive) and Streptococcus (Catalase negative). +ve Catalase test = Bubble formation due to release of nascent O2 from H2O2 by Catalse enzyme in the colony Catalase positive organisms Staphylococcus Pseudomonas aeruginosa Aspergillus fumigatus Candida Enterobacteriaceae except Shigella dysentry type 1