Morphometric and biological characterization of biofilm in tunneled hemodialysis catheters

Abstract

Background: Bacterial biofilm formation on hemodialysis tunneled cuffed catheters is under-recognized. We studied biofilm characteristics in patients with and without catheter-related bloodstream infection, accounting for catheter locking solution (citrate 4% or heparin 1:1,000).

Study design: Prospective observational study.

Setting & participants: 30 HD patients for whom the tunneled cuffed catheter was removed for either noninfectious reasons (n = 19) or bacteremia (n = 11).

Predictors: Bacteremia and catheter locking solution.

Outcomes & measurements: Bacteria density in the biofilm, catheter luminal surface covered by biofilm, biofilm thickness, and exopolysaccharide content.

Results: Biofilm was present in all catheters. Overall, bacteria density, catheter surface coverage, biofilm thickness, and exopolysaccharide content were significantly higher in catheters from patients with bacteremia (5.3 [95% CI, 3.4-7.2] colony-forming unit [CFU]/mL; 47% [95% CI, 34%-60%]; 41 [95% CI, 26-55] μm; and 29.4% [95% CI, 20.1%-38.6%], respectively) than from patients without bacteremia (3.7 [95% CI, 3.6-3.8] CFU/mL; 17% [95% CI, 16%-19%]; 8.6 [95% CI, 7.3-9.8] μm; and 5.3% [95% CI, 3.7%-6.8%], respectively). However, all biofilm parameters were lower in catheters from patients with bacteremia when citrate was used as locking agent. Furthermore, bacteria density (0.08 [95% CI, 0.02-0.13] CFU/mL/3 cm), biofilm thickness (1.4 [95% CI, 0.8-2.1] μm/3 cm), and surface coverage (2.2% [95% CI, 1.8%-2.7%]/3 cm) decreased across the length of the catheter from tip to hub.

Limitations: Observational study design, small numbers of patients, use of prevalent catheters.

Conclusion: Biofilms are present in all tunneled cuffed catheters. However, the extent of the biofilm varied by the presence of bacteremia and type of locking solution. This method could be used to explore preventative measures.