## **Core Concept**
Catheter-related bloodstream infections (CRBSIs) are a significant concern in healthcare settings, particularly in intensive care units (ICUs) and among patients requiring long-term intravenous therapy. These infections occur when microorganisms enter the bloodstream through the insertion site of an intravascular catheter or through the catheter hub. The most common pathogens responsible for CRBSIs are typically bacteria.

## **Why the Correct Answer is Right**
The correct answer, **Coagulase-negative staphylococci (CONS)**, particularly *Staphylococcus epidermidis*, is a common cause of CRBSIs. This organism is part of the normal skin flora and can easily colonize catheters during insertion or through the catheter hub. CONS are known for their ability to form biofilms on catheter surfaces, making them difficult to eradicate and a common cause of CRBSIs.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While *Staphylococcus aureus* can cause CRBSIs and is a significant pathogen due to its virulence and potential to cause metastatic infections, it is not the most common cause compared to CONS.
- **Option B:** *Candida* species are an important cause of CRBSIs, particularly in patients receiving total parenteral nutrition or having been on broad-spectrum antibiotics. However, they are less common than bacterial causes like CONS.
- **Option D:** *Pseudomonas aeruginosa* can cause CRBSIs, especially in certain populations like immunocompromised patients or those with long-term catheters. However, it is not as frequently encountered as CONS.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the prevention of CRBSIs involves strict adherence to aseptic insertion and maintenance protocols, including proper hand hygiene, use of chlorhexidine for skin preparation, and removal of catheters when no longer necessary. The most common pathogens like CONS highlight the importance of sterile technique.

## **Correct Answer:** . **Coagulase-negative staphylococci**