Effects of Lipid Emulsion and Multivitamins on the Growth of Microorganisms in Peripheral Parenteral Nutrition Solutions

BACKGROUND Blood stream infections caused by Bacillus cereus or Serratia marcescens in patients receiving peripheral parenteral nutrition (PPN) have occasionally been reported in Japan, but these microorganisms are not major causes of blood stream infections in patients receiving total parenteral nutrition via a central venous catheter. In Japan, commercially available PPN solutions contain amino acids, glucose, and electrolytes, but not contain lipid emulsion (LE) and multivitamins (MV). In this study, the effects of LE and MV on the growth of microorganisms such as Bacillus cereus, Serratia marcescens, Staphylococcus aureus, and Candida albicans in PPN solutions were investigated. METHODS A commercial 3% amino acid and 7.5% glucose solution with electrolytes (AF) was used as the base solution to prepare test solutions (LAF, AFV, and LAFV) containing LE, MV, or both. Specifically, 20% LE was added to AF in a ratio of 1:9 to prepare LAF. MV was added to AF and LAF to prepare AFV and LAFV, respectively. A specified number of each microorganism was added to each 100 mL of AF, LAF, AFV, and LAFV in sterile plastic flasks, and all flasks were allowed to stand at room temperature. The number of colony forming units per mL of each microorganism was counted at 0, 24, and 48 hours after the addition of each microorganism. RESULTS Both Bacillus cereus and Serratia marcescens increased rapidly in AF as well as in LAF, AFV, and LAFV. Staphylococcus aureus did not increased in AF, but increased slightly in LAF and increased rapidly in AFV and LAFV. Candida albicans increased slightly in AF and increased rapidly in LAF, AFV, and LAFV. CONCLUSIONS The results suggest the followings: if microbial contamination occurs, 1) Bacillus cereus and Serratia marcescens can grow rapidly in PPN solutions consisting of amino acids, glucose and electrolytes; 2) Staphylococcus aureus cannot grow without LE and MV, but can grow rapidly with MV; 3) Candida albicans can grow slowly without LE and MV, and the addition of LE or MV accelerates its growth.