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Growth of Staphylococcus aureus in Diprivan and Intralipid: implications on the pathogenesis of infections
P B Langevin1, N Gravenstein, T J Doyle
1Department of Anesthesiology, University of Florida College of Medicine, Gainesville, USA. anita@anest2.anest.ufl.edu
Background:
The incidence and severity of infections are increased when Intralipid or Diprivan are administered to patients. Intralipid promotes infection, presumably by inhibiting the reticuloendothelial system, thereby suppressing the host's constitutive immunity, whereas Diprivan supposedly promotes infection by supporting bacterial growth and increasing the inoculating dose. This study considers whether bacterial replication alone in Intralipid and Diprivan adequately explains the increased risk of infection associated with these agents or whether other factors might also be involved.
Methods:
Staphylococcus aureus was cultured in 10% Intralipid or Diprivan at clinically relevant conditions or in Intralipid containing 0.005% (w/v) sodium EDTA, a current additive, to measure growth. To determine whether Intralipid affected infection, New Zealand white rabbits were injected intravenously with S. aureus with or without Intralipid. Twenty-four hours later, bacteria in lung, liver, spleen, and kidney tissues were enumerated.
Results:
S. aureus failed to grow in Diprivan or Intralipid containing 0.005% EDTA. Whereas S. aureus did replicate in plain Intralipid, growth was delayed until the bacteria conditioned the media. Once initiated, growth was slow at clinically relevant temperatures. The administration of Intralipid to rabbits significantly increased the recovery of staphylococci from the kidneys, P < 0.001, relative to the other tissues 24 h after an intravenous inoculation with S. aureus, compared with rabbits receiving S. aureus with no Intralipid.
Conclusions:
These results suggest that Diprivan, and possibly Intralipid, represent poor media for the growth of S. aureus and may promote infection through mechanisms other than increased inoculum size.
Insights
Intralipid and Diprivan may increase infection risk through mechanisms beyond bacterial growth. Studies show Staphylococcus aureus replicates poorly in these agents, suggesting other factors contribute to infection.
Area of Science:
- Microbiology
- Immunology
- Pharmacology
Background:
- Intralipid and Diprivan administration is linked to increased infection incidence and severity.
- Intralipid may suppress host immunity by inhibiting the reticuloendothelial system.
- Diprivan is suspected to promote infection by supporting bacterial growth and increasing inoculum size.
Purpose of the Study:
- To investigate if bacterial replication in Intralipid and Diprivan adequately explains increased infection risk.
- To explore potential alternative mechanisms contributing to infection risk with these agents.
Main Methods:
- Cultured Staphylococcus aureus in Intralipid and Diprivan under clinical conditions.
- Assessed bacterial growth in Intralipid with and without EDTA.
- Injected rabbits with S. aureus and Intralipid to evaluate infection development and bacterial load in tissues.
Main Results:
- Staphylococcus aureus did not grow in Diprivan or Intralipid with EDTA.
- Bacterial growth in plain Intralipid was delayed and slow, occurring after media conditioning.
- Intralipid administration significantly increased S. aureus recovery in rabbit kidneys.
Conclusions:
- Diprivan and Intralipid appear to be poor growth media for Staphylococcus aureus.
- Mechanisms other than increased bacterial inoculum size likely contribute to the infection risk associated with Diprivan and Intralipid.