This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
Most common catheter-related bloodstream infection is - 
Select and explain. 
A. Candida, B. Gram negative organisms, C. Coagulase positive staphylococci, D. Coagulase negative staphylococci
D: Coagulase negative staphylococci
Answer: D: Coagulase negative staphylococci 
Explanation: "The most common pathogens isolated from vascular device-associated bacteremia include coagulase-negative staphylococci, S. aureus, enterococci, nosocomial gram-negative bacilli and candida."
"Staph aureus is second only to CoNS as a cause of primary nosocomial bacteremia" 
So:

M.C. cause of catheter-related bloodstream infection → coagulase-negative staphylococci
2nd MC cause of catheter-related bloodstream infection → coagulase-positive staphylococci (S. aureus)