title: Factors Influencing Escherichia coli and Enterococcus durans Growth in Parenteral Nutrition With and Without Lipid Emulsion to Inform Maximum Duration of Infusion Policy Decisions.
abstract: BACKGROUND
  Recommendations effectively restrict the infusion duration of lipid-containing parenteral nutrition (PN) from a single bag, purportedly because it encourages growth of potential microbial contaminants more than lipid-free PN. Since other variables, including osmolarity, may independently affect microbial growth, this study examined variables affecting growth of Escherichia coli and Enterococcus durans in PN infusates.
  
  
  METHODS
  Growth of E coli and E durans was assessed in quadruplicate in 12 different PN infusates, with and without lipid, in varying glucose concentrations.
  
  
  RESULTS
  Results are presented as mean log10 colony-forming units (cfu)/mL ± SEM at 48 hours. The log10cfu/mL of both E coli and E durans in PN increased considerably after adjustment for baseline log10cfu/mL and pH, from 1.093 to 2.241 (P < .001) and from 0.843 to 3.451 (P < .001) respectively. Growth of each microorganism was independently increased by lipid inclusion, or increasing the proportion of nonnitrogen energy from lipid, and reduced by raising the glucose concentration or energy density. Increasing the osmolarity of lipid-PN with glucose or sodium chloride reduced growth but only significantly for sodium chloride (E coli, P = .025; E durans, P = .045). Induced changes in pH affected the growth of the 2 organisms differently.
  
  
  CONCLUSIONS
  The presence of lipid and an increasing proportion of energy from lipid in PN favored the growth of E coli and E durans. Osmolarity changes and the nutrient type causing these changes independently affect the growth of these microbes. Each effect needs to be considered when establishing guidelines based on the growth of potential contaminants in different types of PN.
authors: Faculty of Medicine, University of Southampton, UK Southampton Pharmacy Research Centre, University Hospital Southampton NHS Foundation Trust, Southampton, UK Peter.Austin@uhs.nhs.uk.
authors: Peter David
authors: PD
authors: Austin
authors: Southampton Pharmacy Research Centre, University Hospital Southampton NHS Foundation Trust, Southampton, UK Faculty of Health Sciences, University of Southampton, Southampton, UK.
authors: Kieran Sean
authors: KS
authors: Hand
authors: Faculty of Medicine, University of Southampton, UK Institute of Human Nutrition, University of Southampton, Southampton, UK.
authors: Marinos
authors: M
authors: Elia
mesh_terms: D003657:Decision Making; D002149:Energy Intake; D016983:Enterococcus / Q000254:growth & development*; D004926:Escherichia coli / Q000254:growth & development*; D005217:Fat Emulsions, Intravenous / Q000008:administration & dosage* / Q000009:adverse effects; D005947:Glucose / Q000008:administration & dosage*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007263:Infusions, Parenteral; D008055:Lipids / Q000008:administration & dosage* / Q000009:adverse effects; D009994:Osmolar Concentration; D010288:Parenteral Nutrition / Q000009:adverse effects; D057766:Policy; D018805:Sepsis / Q000209:etiology / Q000382:microbiology*; D012965:Sodium Chloride / Q000008:administration & dosage
chemical_list: D005217:Fat Emulsions, Intravenous; D008055:Lipids; D012965:Sodium Chloride; D005947:Glucose
keywords: administration; outcomes research/quality; parenteral nutrition; sepsis