How does catheter bloodstream infection occur?

Catheter bloodstream infection actually means that the patient has fungemia. The most obvious symptom of this disease is fever. There are many reasons for catheter bloodstream infection, such as extracavitary route contamination, intracavitary route contamination, connector and fluid contamination, etc. You may as well take relevant preventive measures based on these causes.

Catheter Related Blood Stream Infection (CRBSI) refers to the occurrence of bacteremia or fungemia in patients with intravascular catheters or within 48 hours of removal of intravascular catheters, accompanied by infection symptoms such as fever (>38°C), chills or hypotension, with no other clear source of infection except the vascular catheter.

Laboratory microbiological examinations showed: peripheral venous blood culture was positive for bacteria or fungi; or pathogens of the same type and with the same drug sensitivity results were cultured from the catheter segment and peripheral blood.

1. Pathogenesis of CRBSI 1. Extracavitary contamination:

Most central venous catheter (CVC) infections are caused by migration of skin-colonizing bacteria. The bacteria come from around the skin puncture site. Due to the capillary action of the puncture tract, the bacteria have a tendency to penetrate into the body, and the electrostatic effect adsorbs the bacteria to the outer wall of the catheter. Bacterial translocation and growth have been reported within 7-9 days after intubation.

2. Intracavitary contamination:

Thrombosis: After the catheter is implanted, the wound surface is wrapped by plasma tissue proteins, and fibrin is deposited on the inner wall of the catheter. Bacteria can adhere to it and quickly form a biofilm to protect it from being phagocytosed by the body, forming thrombi and developing into bacterial translocation growth and infection.

Connector and fluid contamination: In clinical nursing work, any aseptic technique errors in diagnosis and treatment using intravenous catheters can allow pathogens to enter the cavity through contaminated connectors or fluids and colonize. Infections with Gram-negative bacilli and Pseudomonas are often associated with contamination of infusion solutions.

Endogenous contamination: Bacteria come from infection foci in other parts of the body. The bacteria can be implanted in the fibrous sheath formed at the tip of the tube through the bloodstream and cause infection. This is common in patients receiving long-term total parenteral nutrition support in the ICU.

2. Determinants of CRBSI

1. Catheter material:

Catheters made of polyethylene and polyvinyl chloride are more susceptible to pathogen adhesion than catheters made of Teflon, silicone, and polyurethane. Some materials have irregular surfaces that favor the adhesion of certain types of pathogens, such as coagulase-negative Staphylococci, Acinetobacter calcobonatus, and Pseudomonas aeruginosa; catheters made from these materials are particularly susceptible to bacterial colonization and secondary infection. As a result, polyethylene and polyvinyl chloride are no longer used in most catheters sold in some countries.

2. Characteristics and virulence of infectious pathogens:

The adhesion characteristics of pathogens are an important mechanism for the pathogenesis of catheter-related infections. For example, Staphylococcus aureus and coagulase-negative staphylococci often adhere to host proteins on the catheter surface. In addition, some strains of coagulase-negative staphylococci can produce an extracellular polysaccharide slime that can enhance bacterial pathogenicity by helping the bacteria resist host defense mechanisms and reducing susceptibility to antibiotics.