In vitro quantitative model of catheter infection during simulated parenteral nutrition.

We developed a quantitative in vitro model of catheter infection. Colonization was initiated by inoculating the catheter lumen with a small number of bacteria (approximately 5 x 10(3) viable organisms). Then the inoculated catheters were used for simulated total parenteral nutrition therapy consisting of infusions for 9 h a day, and bacteria were counted in the effluent fluid against time, enabling us to monitor catheter colonization quantitatively. Bacterial colonization of prosthetic devices is a progressive process, as evidenced by the slow day-to-day increase of bacterial release seen here. On the other hand, bacterial strains of various representative species exhibited significant differences in their ability to infect catheters. These results suggest that the in vitro model presented here is a reliable tool for monitoring the degree of catheter colonization under standardized conditions and could be used for further studying the main factors of catheter-related sepsis or the treatment of this information.