Identification of central venous hemodialysis catheter-related infection by a semiquantitative culture method

Central venous hemodialysis catheter-related infection is a major cause of morbidity and mortality in the hemodialysis (HD) population. Due to an impaired immune response, symptoms and signs of infection may not be obvious, and thus bacteremia is often diagnosed and treated protractedly. In contrast, induction of the acute phase response is frequently observed in HD patients even without infection. Moreover, positive catheter cultures may result from contamination, asymptomatic colonization or infection. The aim of the present study was to compare the number of colonies from HD catheter tips, with symptoms and signs of infection in HD patients.

In a 10-year, single-center study, 53 HD patients (29 men, 24 women; mean age 66 +/- 10 years) who had their dialysis catheters removed were divided into 3 groups according to the number of colonies growing after rolling the catheter tip across blood agar (group I: <15 colonies [n=22], II: 15-50 colonies [n=15], III: >50 colonies [n=16]).

The maximum white blood cell (WBC) count did not differ significantly between patients with low- and high-density colonization (group I: 11.746 +/- 9.680 WBC/microL vs. group III: 13.479 +/- 6.252 WBC/microL, p=NS) while maximum C-reactive protein (CRP) levels were higher in patients with high-density colonization (group I: 8.6 +/- 6.8 vs. group III: 19.2 +/- 12.2 mg/dL, p<0.05). Density of bacterial colonization was associated with the maximum body temperature (group I: 37.6 degrees C +/- 1.1 degrees C vs. 38.7 degrees C +/- 0.9 degrees C, p<0.05). Moreover patients with high-density colonization showed increased bacteremia (group I: 33% vs. group III: 93%, p<0.01) as well as an increased mortality due to septicemia (group I: 9% vs. group III: 50%, p<0.01). Patients of group II exhibited intermediate values in all analyses.

The semiquantitative culture technique can help to differentiate between contamination and infection of central venous HD catheters and provides important prognostic information in dialysis patients.