Microbial growth patterns in a total parenteral nutrition formulation containing lipid emulsion

Microbial growth of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans was evaluated in a standard amino acid-dextrose-based total parenteral nutrition (TPN) solution, 10% lipid emulsion, and a combined TPN formulation containing amino acids, dextrose, and lipid emulsion. At an initial inoculum of 10(4) CFU/ml, all three bacterial organisms grew well in 10% lipid emulsion, died in the standard solution and grew only minimally or died in the combined formulation. C. albicans grew in all three formulations at an initial inoculum of 10(4) CFU/ml; however, at an initial inoculum of 10(2) CFU/ml, which approximates touch contamination, growth of Candida in the standard and combined formulations was less than 1 log at 24 hr in contrast to the 10% lipid emulsion which showed significant growth greater than 2 log at 24 hr. It is concluded that a 24-hr infusion time is safe for the combined TPN formulation used in this study. This should result in significant cost savings compared to the previously recommended 12-hr infusion time.