This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Peritoneum, Subject name: Surgery
A 60 years old diabetic male developed renal failure. The family belonged to lower middle class, was not able to afford hemodialysis frequently. Chronic ambulatory peritoneal dialysis (CAPD) was being performed. After 4 months of CAPD, the patient developed peritonitis. What is the most common organism responsible? 
Select and explain. 
A. Staph. aureus, B. Staph. epidermidis, C. E. coli, D. Bacteroides
B: Staph. epidermidis
Answer: B: Staph. epidermidis 
Explanation: CAPD: Continuous Ambulatory Peritoneal Dialysis Catheter MC colonised by: Staph epidermidis Rx: First gen cephalosporins catheter Recurrent attacks: change the catheter