Factors that influence Staphylococcus epidermidis growth in parenteral nutrition with and without lipid emulsion: a study framework to inform maximum duration of infusion policy decisions

Abstract

Background & aims: Recommendations limit infusion of parenteral nutrition (PN) from bags with lipid to 24 h (48 h if lipid free) because lipid putatively encourages contaminant growth. This study aimed to examine these recommendations and identify factors affecting Staphylococcus epidermidis growth in PN.

Methods: S. epidermidis growth was assessed in quadruplicate in 12 PN regimens, with and without lipid and varying glucose concentrations.

Results: Baseline colony forming units (cfu)/mL (32.6) less than doubled at 48 h in all infusates. In PN infusates (pH 6.2 + 0.02 (SEM)) growth was independently increased by the presence of 5% w/v lipid (14.2 cfu/mL; P = 0.028), and glucose concentration (25.6 cfu/mL per 10% increase in w/v glucose; P = 0.003). In a separate analysis growth was stimulated by energy density (27.7 cfu/1000 kcal non-nitrogen energy in 2 L; P = 0.002), without a significant effect of % non-protein energy from lipid (-2.6 cfu/ml per 10%).

Conclusions: Using a framework developed to examine growth of potential contaminants in PN, no evidence was found to support the specific recommendation to restrict the maximum infusion duration of lipid containing PN to a greater extent than lipid free PN. S. epidermidis growth was not only affected by the presence of lipid, but also glucose concentration and energy density.