This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Kidney, Subject name: Medicine
Most common organism involved in urinary catheter induced urinary tract infection is - 
Select and explain. 
A. E.coli, B. Pseudomonas, C. Staphylococcus epidermidis, D. Proteus
A: E.coli
Answer: A: E.coli 
Explanation: Most commonly involved organism in causing urinary tract infection is E. Coli. Risk factors - More common in females Recent use of a diaphragm with spermicide, frequent sexual intercourse. Maternal history of diabetes ,UTI and incontinence . Obstruction in urine flow(calculi,malignancies) Incomplete voiding(residual urine) Foriegn body in urinary tract (catheter, calculi) Ref:Harrison 20 th edition pg no 969,970