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Effects of isoflurane on bacterial growth
K Asehnoune1, P Cruaud, J Paries
1Department of Anaesthesia and Intensive Care, CHU Jean Verdier-Université Paris XIII, Bondy, France.
Abstract:
Anaesthetic agents have been implicated in the development of postoperative pneumonia, but the direct effect of volatile anaesthetics on bacterial growth has given contradictory results. The effects of isoflurane on the growth of Staphylococcus aureus and Escherichia coli were investigated under conditions similar to those of clinical practice, using standardized microbiological methods. An open anaesthetic circuit was adjusted to the normal ventilatory settings of an adult patient. A spray, installed on the inspiratory side of the circuit, ensured the delivery of isoflurane at 1.5 minimal alveolar concentration. The bacterial strains studied were both wild-type and reference strains. Bacterial inoculums were prepared to obtain a bacterial exponential growth of 10(3) colony-forming units per mL in 10 mL of nutritive broth. Each strain was studied with and without exposure to isoflurane and measured by the usual criteria of bacterial growth, and by bacterial regrowth after exposure to isoflurane. Under experimental conditions close to clinical practice, exposure to isoflurane did not alter bacterial growth of S. aureus and E. coli, or their bacterial regrowth when isoflurane exposure is over.
Insights
This study found that isoflurane, a common anesthetic, does not affect the growth or regrowth of Staphylococcus aureus and Escherichia coli. These findings suggest isoflurane does not directly impact bacterial proliferation in clinical settings.
Area of Science:
- Anesthesiology
- Microbiology
- Infectious Diseases
Background:
- Volatile anesthetics are suspected contributors to postoperative pneumonia.
- Previous research on volatile anesthetics' direct impact on bacterial growth yielded conflicting results.
Purpose of the Study:
- To investigate the direct effects of isoflurane on the growth and regrowth of Staphylococcus aureus and Escherichia coli.
- To assess bacterial response to isoflurane under conditions mimicking clinical anesthesia practice.
Main Methods:
- Standardized microbiological methods were employed.
- Bacterial strains (Staphylococcus aureus, Escherichia coli) were exposed to 1.5 minimal alveolar concentration of isoflurane in an open anesthetic circuit.
- Bacterial growth and regrowth were measured using standard criteria.
Main Results:
- Exposure to isoflurane did not alter the growth of Staphylococcus aureus or Escherichia coli.
- Bacterial regrowth after isoflurane exposure was also unaffected in both bacterial species.
Conclusions:
- Under conditions simulating clinical practice, isoflurane does not directly inhibit or promote the growth of Staphylococcus aureus and Escherichia coli.
- The study suggests that isoflurane itself is unlikely to be a direct cause of altered bacterial proliferation contributing to postoperative pneumonia.