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
Which of the following is not an AB 5 toxin- 
Select and explain. 
A. Cholera toxin, B. Pertussis toxin, C. Shiga toxin, D. Heat labile toxin
B: Pertussis toxin
Answer: B: Pertussis toxin 
Explanation: Ans. B. Pertussis toxin.a. Pertussis toxin is a 105 kDa protein composed of six subunits:b. S1 (A subunit) and B subunit consisting of S2, S3, (2) S4, and S5.c. Pertussis toxin is the most important virulence factor- helps it to evade phagocytes by inhibiting their phagocytic function and helps the bacterium to bind host cells.