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Characteristics of biofilm on tunneled cuffed hemodialysis catheters in the presence and absence of clinical infection.

BACKGROUND
Biofilm occurring on the surface of tunneled hemodialysis (HD) catheters is difficult to eradicate and often is associated with recurrent bacteremia. We studied biofilm formation on catheters from patients with and without bacteremia to identify the location of bacterial growth and measure biofilm thickness.


STUDY DESIGN
Prospective observational study.


SETTING & PARTICIPANTS
76 adult HD patients; 26 had HD catheters removed for bacteremia and 50 had catheters removed for reasons other than infection.


PREDICTORS
Segment of catheter, reason for catheter removal.


OUTCOMES & MEASUREMENTS
Microbiological growth and biofilm thickness on the outer and luminal surfaces of extravascular and intravascular catheter segments.


RESULTS
Catheter cultures were positive in 16 (62%) patients with bacteremia and 15 (30%) when the catheter was removed for non-infection-related reasons. In catheters with positive cultures, the outer surface of the extravascular segment was the most common site of bacterial growth (15/16 [94%] and 11/15 [73%] for bacteremic and nonbacteremic patients, respectively). Bacteremic patients had significantly thicker biofilm on all catheter surfaces, and in bacteremic patients, the biofilm was significantly thicker on the outer compared with the luminal surface for both extravascular (14.53 ± 6.17 vs 11.97 ± 5.01 μm; P < 0.001) and intravascular (12.21 ± 5.3 vs 9.46 ± 3.71 μm; P < 0.001) segments. Extravascular segments had significantly thicker biofilm compared with intravascular segments on both the outer (P < 0.001) and luminal (P < 0.001) surfaces. Similarly, in patients for whom the catheter was removed for non-infection-related reasons, the catheter had thicker biofilm on the outer compared with the inner surface in both extravascular (2.19 ± 2.84 vs 1.62 ± 2.33 μm; P < 0.001) and intravascular (1.92 ± 2.62 vs 1.29 ± 2.33 μm; P < 0.001) segments. Similar to catheters from bacteremic patients, the outer and luminal surfaces of the extravascular segments of the catheters had significantly thicker biofilm compared with their corresponding surfaces on the intravascular segments.


LIMITATIONS
Observational study.


CONCLUSIONS
The outer surface of the extravascular segment of tunneled dialysis catheters in both bacteremic and nonbacteremic HD patients has the thickest biofilm and highest microbiological yield, and biofilm is thicker in patients with bacteremia. This knowledge is important for designing preventive strategies and also in the management of patients with catheter infection.