This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Lab Investigations, Subject name: Microbiology
Surface antigen of E coli acting as virulence factors are:- 
Select and explain. 
A. LPS O Antigen, B. Capsular K antigen, C. Fimbriae, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Virulence factors of E. coli: Surface antigens Toxins Somatic or O ag- Lipopolysaccharide (LPS), most impoant virulence factor & responsible for endotoxic activities LT (heat labile toxin) - - | cAMP so causes excessive secretion of Na/Cl/H2O from within to outside the cell = secretory diarrhea Flagellar or H Ag- Makes the bacteria motile. ST (heat stable toxin)- - | cGMP so fluid accumulation in gut = Diarrhea Capsular or K Ag- It is a polysaccharide capsular Ag, inhibits the phagocytosis. Verocytotoxin or Shiga like toxin - - It inhibits the protein synthesis by binding to 28S subunit of 60S ribosome = Cell death Fimbrial antigen (Pilus) - helps in attachment & colonization.