This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteriology, Subject name: Microbiology
Streptococcus pyogenes is 
Select and explain. 
A. Gram positive cocci, B. Gram negative cocci, C. Gram positive bacilli, D. Gram negative bacilli
A: Gram positive cocci
Answer: A: Gram positive cocci 
Explanation: Streptococci are the gram-positive cocci arranged in chains or pairs. Gram-positive cells have a more acidic protoplasm, which may account for retaining the basic primary dye more strongly than gram-negative bacteria. Gram-positive bacteria are those that resist decolorization and retain the primary stain appearing violet. Reference: Textbook of Microbiology; Anathanarayan and paniker's; 10th edition; Page no: 13, 210