title: Systematic review and meta-analyses of the effect of lipid emulsion on microbial growth in parenteral nutrition.
abstract: BACKGROUND
  As lipid in parenteral nutrition (PN) purportedly enhances microbial growth, recommendations limit infusion of lipid PN (or lipid emulsion) from a single container to 24h (48h for lipid-free PN). However, the associated evidence base is ambiguous.
  
  
  OBJECTIVE
  To examine factors affecting microbial growth in PN.
  
  
  METHODS
  A systematic review with meta-analyses examined effects of nutrients on microbial growth in PN infusates over a 48-h period using the growth ratio {GR=log10[colony-forming units (cfu)/mL at 48h/cfu/mL at time zero]}.
  
  
  RESULTS
  Factors influencing GR in PN included glucose, microbial species, temperature, osmolarity, presence of vitamins, trace elements and lipid, and amino acid profile. Using unmatched datasets (N=306), a general linear model found that lipid inclusion in PN represented 3.3% of the variability, which was less than that due to glucose concentration (5.8%), microbial species (35.3%) and microbe-infusate interaction (4.4%). Using matched datasets (N=38 pairs), lipid inclusion in PN represented 5.4% of the variability (P=0.076), which was less than that due to glucose concentration (8.5%; P=0.025), microbial species (75.5%; P<0.001) and microbe-infusate interaction (13.3%; P=0.382). Using meta-analyses of matched datasets, the presence of lipid in PN at fixed glucose concentrations did not significantly increase GR of Candida albicans, Escherichia coli or Staphylococcus epidermidis (P=0.352, P=0.025 and P=0.494, respectively; overall P=0.175).
  
  
  CONCLUSIONS
  Lipid inclusion in PN is only one of several factors that may influence microbial growth in PN. Any recommendations about the duration of PN infusion from a single container should account for all these factors, and should be weighted according to microbial species likely to contaminate PN.
authors.affiliation: Faculty of Medicine, University of Southampton, Southampton, UK; Southampton Pharmacy Research Centre, University Hospital Southampton NHS Foundation Trust, Southampton, UK; Pharmacy Department, Oxford University Hospitals NHS Foundation Trust, Oxford, UK. Electronic address: Peter.Austin@ouh.nhs.uk.
authors.forename: P D
authors.initials: PD
authors.lastname: Austin
authors.affiliation: Southampton Pharmacy Research Centre, University Hospital Southampton NHS Foundation Trust, Southampton, UK; Faculty of Health Sciences, University of Southampton, Southampton, UK.
authors.forename: K S
authors.initials: KS
authors.lastname: Hand
authors.affiliation: Faculty of Medicine, University of Southampton, Southampton, UK; Institute of Human Nutrition, University of Southampton, Southampton, UK; National Institute for Health Research Southampton Biomedical Research Centre, University Hospital Southampton NHS Foundation Trust, Southampton, UK.
authors.forename: M
authors.initials: M
authors.lastname: Elia
mesh_terms: D001419:Bacteria / Q000254:growth & development*; D002176:Candida albicans / Q000254:growth & development*; D004655:Emulsions / Q000008:administration & dosage; D006801:Humans; D008055:Lipids / Q000008:administration & dosage*; D010288:Parenteral Nutrition
chemical_list: D004655:Emulsions; D008055:Lipids
keywords: Catheter infection; Lipid; Microbial growth; Parenteral nutrition; Sepsis; Venous access