DIAGNOSIS OF TRIPLE-LUMEN CATHETER INFECTION - COMPARISON OF ROLL PLATE, SONICATION, AND FLUSHING METHODOLOGIES

In a recent clinical trial, 248 triple-lumen catheters were removed fr om patients in an intensive care unit, and their tip and subcutaneous segments were cultured by both the sonication and roll plate methods; for 191 of these catheters, flush cultures of all three catheter lumen s were also performed. Previously published quantitative endpoints wer e used to define significant catheter colonization. By using a composi te index as a definition of colonization (any of the seven types of cu ltures meeting quantitative criteria), sonication of the subcutaneous segment was the most sensitive at detecting colonization (58%), follow ed by sonication of the catheter tip (53%). Sonication of both the sub cutaneous and tip segments was 20% more sensitive than sonication of a n adjacent catheter segment by the roll plate method (P < 0.05). The g reater sensitivity of the sonication method could be attributed to its greater ability than the roll plate method to detect catheter lumen c olonization (82 versus 57%, respectively; P = 0.01). A greater number of positive catheter segment cultures were found for colonized cathete rs from patients with associated bacteremia than for colonized cathete rs from patients without bacteremia (57 versus 37%; P = 0.004), making any culture method more likely to identify them. For catheters with s ignificant colonization of only one site, the localization was as foll ows: 36.7% subcutaneous segment, 36.7% catheter lumen, and 26.6% tip s egment. These findings suggest that the current practice of culturing a single segment of a central vascular catheter is inadequate and need s to be reexamined. They further suggest that initial colonization of the catheter lumen and tip segments may be more important than previou sly thought and may require a change in thinking of strategies designe d to prevent catheter infection.