Microbial growth comparisons of five commercial parenteral lipid emulsions

The ability of parenteral lipid emulsions to support microbial growth was compared using commercially available brands of lipid emulsion. Both 10 and 20% concentrations of soybean and safflower oil emulsions were used. Washed cultures of six gram-negative, three gram-positive, and one yeast, in concentrations of 1 x 10(4) to 2 x 10(4) colony-forming units/ml, were inoculated into lipid emulsion aliquots and stored at room temperature. There were than subcultured at 0, 6, 12, 24 and 48 hr. After 48 hr at 37 degrees C, growth was recorded as colony-forming units/ml. Normalized growth curves were expressed as mean +/- SEM. ANOVA demonstrated no difference in growth patterns due to the nature of the oil or its concentration. Gram-negative organisms multiplied faster when compared to gram-positive (p less than 0.05 at 12 hr, p less than 0.01 at 24 hr, and p less than 0.005 at 48 hr). Yeast grew as well as bacteria. The Center for Disease Control's recommendation of a 12-hr hang time for parenteral lipid emulsions should be observed until correlation of laboratory microbial growth patterns and clinical use are studied further.