Limits...
Escherichia coli morphological changes and lipid A removal induced by reduced pressure nitrogen afterglow exposure.

Zerrouki H, Rizzati V, Bernis C, Nègre-Salvayre A, Sarrette JP, Cousty S - PLoS ONE (2015)

Bottom Line: Previous studies have demonstrated that the late afterglow region of flowing post-discharges at reduced pressure (1-20 Torr) can be used for the sterilization of surfaces and of the reusable medical instrumentation.In the present paper, we show that the antibacterial activity of a pure nitrogen afterglow can essentially be attributed to the large concentrations of nitrogen atoms present in the treatment area and not to the UV radiation of the afterglow.The afterglow exposure also results in a reduction of the lipid A proinflammatory activity, assessed by the net decrease of the redox-sensitive NFκB transcription factor nuclear translocation in murine aortic endothelial cells stimulated with control vs afterglow-treated (pure and extracted) lipid A.

View Article: PubMed Central - PubMed

Affiliation: Université de Toulouse, UPS, INPT, LAPLACE (Laboratoire Plasma et Conversion d'Energie), Bât. 3R2, F-31062, Toulouse, France; CNRS, LAPLACE, F-31062 Toulouse, France.

ABSTRACT
Lipid A is a major hydrophobic component of lipopolysaccharides (endotoxin) present in the membrane of most Gram-negative bacteria, and the major responsible for the bioactivity and toxicity of the endotoxin. Previous studies have demonstrated that the late afterglow region of flowing post-discharges at reduced pressure (1-20 Torr) can be used for the sterilization of surfaces and of the reusable medical instrumentation. In the present paper, we show that the antibacterial activity of a pure nitrogen afterglow can essentially be attributed to the large concentrations of nitrogen atoms present in the treatment area and not to the UV radiation of the afterglow. In parallel, the time variation of the inactivation efficiency quantified by the log reduction of the initial Escherichia coli (E. coli) population is correlated with morphologic changes observed on the bacteria by scanning electron microscopy (SEM) for increasing afterglow exposure times. The effect of the afterglow exposure is also studied on pure lipid A and on lipid A extracted from exposed E. coli bacteria. We report that more than 60% of lipid A (pure or bacteria-extracted) are lost with the used operating conditions (nitrogen flow QN2 = 1 standard liter per minute (slpm), pressure p = 5 Torr, microwave injected power PMW = 200 W, exposure time: 40 minutes). The afterglow exposure also results in a reduction of the lipid A proinflammatory activity, assessed by the net decrease of the redox-sensitive NFκB transcription factor nuclear translocation in murine aortic endothelial cells stimulated with control vs afterglow-treated (pure and extracted) lipid A. Altogether these results point out the ability of reduced pressure nitrogen afterglows to neutralize the cytotoxic components in Gram-negative bacteria.

No MeSH data available.


Related in: MedlinePlus

Effect of nitrogen afterglow exposure on bacteria inactivation and viability.A: Survival curves obtained for E. coli bacteria exposed to the nitrogen late afterglow with and without the MgF2 filter. B: MTT test in bacteria control (vacuum-treated) vs bacteria exposed to the nitrogen late afterglow. Bacteria were eluted from the slides with 1 ml of Broth medium, and incubated in this medium with the MTT reagent (5 mg/ml). After 3 h incubation at 37°C, the bacteria suspension was centrifuged, and the violet formazan crystals were dissolved in 200 μl of DMSO. The optical density was estimated on a microplaque TECAN reader. C. Pictures of bacteria submitted either to vacuum alone for 15 min (LP), or to vacuum + nitrogen late afterglow (AG), and stained with the nucleic acid fluorescent probe DAPI. The results are expressed as % of the vacuum-treated control. Mean +/-SEM of 5 separate experiments, * < p.0.05.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4383372&req=5

pone.0116083.g002: Effect of nitrogen afterglow exposure on bacteria inactivation and viability.A: Survival curves obtained for E. coli bacteria exposed to the nitrogen late afterglow with and without the MgF2 filter. B: MTT test in bacteria control (vacuum-treated) vs bacteria exposed to the nitrogen late afterglow. Bacteria were eluted from the slides with 1 ml of Broth medium, and incubated in this medium with the MTT reagent (5 mg/ml). After 3 h incubation at 37°C, the bacteria suspension was centrifuged, and the violet formazan crystals were dissolved in 200 μl of DMSO. The optical density was estimated on a microplaque TECAN reader. C. Pictures of bacteria submitted either to vacuum alone for 15 min (LP), or to vacuum + nitrogen late afterglow (AG), and stained with the nucleic acid fluorescent probe DAPI. The results are expressed as % of the vacuum-treated control. Mean +/-SEM of 5 separate experiments, * < p.0.05.

Mentions: The survival curves obtained from CFU counting, with and without the MgF2 filter are shown in Fig. 2A. Results are expressed as % of inactivated bacteria, the reference (100%) corresponding to bacteria exposed to the 5 Torr N2 flux, discharge off.


Escherichia coli morphological changes and lipid A removal induced by reduced pressure nitrogen afterglow exposure.

Zerrouki H, Rizzati V, Bernis C, Nègre-Salvayre A, Sarrette JP, Cousty S - PLoS ONE (2015)

Effect of nitrogen afterglow exposure on bacteria inactivation and viability.A: Survival curves obtained for E. coli bacteria exposed to the nitrogen late afterglow with and without the MgF2 filter. B: MTT test in bacteria control (vacuum-treated) vs bacteria exposed to the nitrogen late afterglow. Bacteria were eluted from the slides with 1 ml of Broth medium, and incubated in this medium with the MTT reagent (5 mg/ml). After 3 h incubation at 37°C, the bacteria suspension was centrifuged, and the violet formazan crystals were dissolved in 200 μl of DMSO. The optical density was estimated on a microplaque TECAN reader. C. Pictures of bacteria submitted either to vacuum alone for 15 min (LP), or to vacuum + nitrogen late afterglow (AG), and stained with the nucleic acid fluorescent probe DAPI. The results are expressed as % of the vacuum-treated control. Mean +/-SEM of 5 separate experiments, * < p.0.05.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4383372&req=5

pone.0116083.g002: Effect of nitrogen afterglow exposure on bacteria inactivation and viability.A: Survival curves obtained for E. coli bacteria exposed to the nitrogen late afterglow with and without the MgF2 filter. B: MTT test in bacteria control (vacuum-treated) vs bacteria exposed to the nitrogen late afterglow. Bacteria were eluted from the slides with 1 ml of Broth medium, and incubated in this medium with the MTT reagent (5 mg/ml). After 3 h incubation at 37°C, the bacteria suspension was centrifuged, and the violet formazan crystals were dissolved in 200 μl of DMSO. The optical density was estimated on a microplaque TECAN reader. C. Pictures of bacteria submitted either to vacuum alone for 15 min (LP), or to vacuum + nitrogen late afterglow (AG), and stained with the nucleic acid fluorescent probe DAPI. The results are expressed as % of the vacuum-treated control. Mean +/-SEM of 5 separate experiments, * < p.0.05.
Mentions: The survival curves obtained from CFU counting, with and without the MgF2 filter are shown in Fig. 2A. Results are expressed as % of inactivated bacteria, the reference (100%) corresponding to bacteria exposed to the 5 Torr N2 flux, discharge off.

Bottom Line: Previous studies have demonstrated that the late afterglow region of flowing post-discharges at reduced pressure (1-20 Torr) can be used for the sterilization of surfaces and of the reusable medical instrumentation.In the present paper, we show that the antibacterial activity of a pure nitrogen afterglow can essentially be attributed to the large concentrations of nitrogen atoms present in the treatment area and not to the UV radiation of the afterglow.The afterglow exposure also results in a reduction of the lipid A proinflammatory activity, assessed by the net decrease of the redox-sensitive NFκB transcription factor nuclear translocation in murine aortic endothelial cells stimulated with control vs afterglow-treated (pure and extracted) lipid A.

View Article: PubMed Central - PubMed

Affiliation: Université de Toulouse, UPS, INPT, LAPLACE (Laboratoire Plasma et Conversion d'Energie), Bât. 3R2, F-31062, Toulouse, France; CNRS, LAPLACE, F-31062 Toulouse, France.

ABSTRACT
Lipid A is a major hydrophobic component of lipopolysaccharides (endotoxin) present in the membrane of most Gram-negative bacteria, and the major responsible for the bioactivity and toxicity of the endotoxin. Previous studies have demonstrated that the late afterglow region of flowing post-discharges at reduced pressure (1-20 Torr) can be used for the sterilization of surfaces and of the reusable medical instrumentation. In the present paper, we show that the antibacterial activity of a pure nitrogen afterglow can essentially be attributed to the large concentrations of nitrogen atoms present in the treatment area and not to the UV radiation of the afterglow. In parallel, the time variation of the inactivation efficiency quantified by the log reduction of the initial Escherichia coli (E. coli) population is correlated with morphologic changes observed on the bacteria by scanning electron microscopy (SEM) for increasing afterglow exposure times. The effect of the afterglow exposure is also studied on pure lipid A and on lipid A extracted from exposed E. coli bacteria. We report that more than 60% of lipid A (pure or bacteria-extracted) are lost with the used operating conditions (nitrogen flow QN2 = 1 standard liter per minute (slpm), pressure p = 5 Torr, microwave injected power PMW = 200 W, exposure time: 40 minutes). The afterglow exposure also results in a reduction of the lipid A proinflammatory activity, assessed by the net decrease of the redox-sensitive NFκB transcription factor nuclear translocation in murine aortic endothelial cells stimulated with control vs afterglow-treated (pure and extracted) lipid A. Altogether these results point out the ability of reduced pressure nitrogen afterglows to neutralize the cytotoxic components in Gram-negative bacteria.

No MeSH data available.


Related in: MedlinePlus