This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteria, Subject name: Microbiology
Not true about streptococcus pyogenes - 
Select and explain. 
A. Gram positive, B. Bacitracin sensitive, C. Catalase positive, D. Not soluble in bile
C: Catalase positive
Answer: C: Catalase positive 
Explanation: Ans. is 'c' i.e., Catalase positiveo Streptococcus pyogenes (group A streptococci) are gram-positive cocci arranged in chains. Chain formation is due to cocci dividing in one plane only and daughter cells failing to separate completely. Chain formation is more pronounced in broth media.o Fresh isolates form capsule which is made up of hyaluronic acid. It protects the organism from phagocytosisCultural characteristicso Virulent strains produce 'matt' (finely granular) colonyo Avirulent strains produce 'glossy' colonies.o Capsulated strains produce mucoid colonies, corresponding in virulence to the matt type.Biochemical reactionso Senstivity to bacitracin is employed as a convenient method for differentiating str. pyogenes from other hemolytic streptococci (Maxted's observation),o Catalase negativeo Not soluble in 10% bile.o Hydrolyse PYRo Ferment trehalose but not ribose.