Effects of parenteral application of fish oil versus soy oil emulsions on bacterial clearance functions

Background: The aim of this study was to test whether or not infusion of tr iglycerides containing omega-3 fatty acids (FAs) modifies immune function i n terms of systemic clearance and organ distribution of injected Escherichi a coli in a rabbit model. Materials and Methods: In groups of 6 rabbits eac h, a defined number of E. coli (1.3 x 10(8) colony-forming units, CFU) was injected intravenously after 3 days of infusion with a lipid emulsion prepa red from fish oil (Omega-venos(R)10%, 1.5 g/kg body weight/day), a soy oil preparation (Lipovenos(R)10%, 1.5 g/kg body weight/day), or after isotonic saline application (control). In order to compare dose-de pendent effects, in a second experimental design a lower dose of each lipid emulsion (0.5 g/ kg body weight) was infused over a 4-hour period before applicating E. coli . Parameters monitored were arterial pressure and rates of bacterial elimin ation from the blood. The animals were killed 3 h and 6 h after bacterial i nfection, respectively, and tissue samples of liver, spleen, lung, and kidn ey were collected for microbiological examinations. Results: Lipovenos infu sion produced a significant delay in blood clearance compared with saline a nd Omegavenos treatment. The diminished systemic bacterial elimination afte r Lipovenos infusion was accompanied by increased numbers af viable bacteri a in lung and spleen. In contrast to this, in the Omegavenos group bacteria l counts in the lung did not increase and smaller amounts of viable bacteri a were detected in organ homogenates 6 h after injection of E. coli Conclus ion: Compared with the soy oil preparation, omega-3 FAs induce improved bac terial clearance from the blood that is associated with significantly lower numbers of E. coli in the lung. Thus, appropriate nutrition providing omeg a-3 FA might serve as a pharmacological tool to improve host defence agains t bacterial infection in critically ill patients.