PGD du projet ANR ”Ressources numériques : offre, intermédiations, réseaux en IUT” (RENOIR-IUT)

Plan de gestion de données créé à l'aide d'OPIDoR, basé sur le modèle "ANR-Modèle de PGD (français)" fourni par Agence nationale de la recherche (ANR)

PGD du projet ANR ”Ressources numériques : offre, intermédiations, réseaux en IUT” (RENOIR-IUT)

Plan de gestion de données créé à l'aide d'OPIDoR, basé sur le modèle "ANR-Modèle de PGD (français)" fourni par Agence nationale de la recherche (ANR)

Mechanical ventilation alters the development of staphylococcus aureus pneumonia in rabbit

Ventilator-associated pneumonia (VAP) is common during mechanical ventilation (MV). Beside obvious deleterious effects on muco-ciliary clearance, MV could adversely shift the host immune response towards a pro-inflammatory pattern through toll-like receptor (TLRs) up-regulation. We tested this hypothesis in a rabbit model of Staphylococcus aureus VAP. Pneumonia was caused by airway challenge with S. aureus, in either spontaneously breathing (SB) or MV rabbits (n = 13 and 17, respectively). Pneumonia assessment regarding pulmonary and systemic bacterial burden, as well as inflammatory response was done 8 and 24 hours after S. aureus challenge. In addition, ex vivo stimulations of whole blood taken from SB or MV rabbits (n = 7 and 5, respectively) with TLR2 agonist or heat-killed S. aureus were performed. Data were expressed as mean +/- standard deviation. After 8 hours of infection, lung injury was more severe in MV animals (1.40 +/- 0.33 versus [vs] 2.40 +/- 0.55, p = 0.007), along with greater bacterial concentrations (6.13 +/- 0.63 vs. 4.96 +/- 1.31 colony forming units/gram, p = 0.002). Interleukin (IL)-8 and tumor necrosis factor (TNF)-alpha serum concentrations reached higher levels in MV animals (p = 0.010). Whole blood obtained from MV animals released larger amounts of cytokines if stimulated with TLR2 agonist or heat-killed S. aureus (e.g., TNF-alpha: 1656 +/- 166 vs. 1005 +/- 89; p = 0.014). Moreover, MV induced TLR2 overexpression in both lung and spleen tissue. MV hastened tissue injury, impaired lung bacterial clearance, and promoted a systemic inflammatory response, maybe through TLR2 overexpression

Inflammatory cytokines in the lung.

<p>Inflammatory cytokines (interleukin [IL]-8 and tumor necrosis factor [TNF]-α) in lung homogenates and in broncho-alveolar lavage fluid (BALF) 8 to 24 hours after tracheal instillation of saline (controls) in either spontaneously breathing (SB, n = 5) rabbits or animals subjected to mechanical ventilation (MV, n = 5), or 8 hours (n = 5) or 24 hours (n = 10) after challenge with 10⁹ CFU of <i>Staphylococcus aureus</i> (+<i>S</i>. <i>aureus</i> H8 and H24). IL-8 levels were increased in lung homogenates and in BALF under MV in controls, but we did not find any significant difference between SB and MV groups after bacterial challenge. Similarly, TNF-α levels were significantly increased in lung homogenates from animals under MV than in controls, but not after bacterial challenge. ** denotes <i>p</i><0.05; ns: not significant; ND: concentration below the limits of detection of the assay. CFU: colony forming unit. (A) Controls SB versus (vs) MV <i>p</i> = 0.333, Mann-Whitney U test, two-tailed. <i>S</i>. <i>aureus</i> H8 SB vs MV p = 0.397, Mann-Whitney U test, two-tailed. <i>S</i>. <i>aureus</i> H24 SB vs MV p = 0.395, Mann-Whitney U test, two-tailed. (B) Controls SB vs MV <i>p</i> = 0.004, Mann-Whitney U test, two-tailed. <i>S</i>. <i>aureus</i> H8 SB vs MV p = 0.413, Mann-Whitney U test, two-tailed. <i>S</i>. <i>aureus</i> H24 SB vs MV p = 0.881, Mann-Whitney U test, two-tailed. (C) Controls SB vs MV <i>p</i> = 0.024, Mann-Whitney U test, two-tailed. <i>S</i>. <i>aureus</i> H8 SB vs MV p = 0.114, Mann-Whitney U test, two-tailed. <i>S</i>. <i>aureus</i> H24 SB vs MV p = 0.700, Mann-Whitney U test, two-tailed. (D) <i>S</i>. <i>aureus</i> H8 SB vs MV p = 0.829, Mann-Whitney U test, two-tailed. <i>S</i>. <i>aureus</i> H24 SB vs MV p = 0.700, Mann-Whitney U test, two-tailed.</p

Pulmonary and systemic bacterial burden of <i>Staphylococcus aureus</i>.

<p><b>(4A)</b><b><i>S</i></b>. <b><i>aureus</i></b><b>lung concentrations 8 and 24 hours after bacteria instillation.</b> Pulmonary bacterial burden according to the experimental group in either spontaneously breathing (SB + <i>S</i>. <i>aureus</i>) or mechanically ventilated (MV + <i>S</i>. <i>aureus</i>) animals with <i>Staphylococcus aureus</i> pneumonia 8 hours after inoculation (n = 5 and 6, respectively) and 24 hours after inoculation (n = 8 and 11 respectively). The bacterial burden was higher in the MV group both after 8 hours (5.00±1.03 versus [vs.] 5.87±0.38 log₁₀CFU/g, <i>p</i> = 0.028) and 24 hours of MV (4.96±1.31 vs. 6.13±0.63 log₁₀CFU/g, <i>p</i> = 0.002). *denotes <i>p</i>≤0.05. CFU: colony forming unit. (4B) <i>S</i>. <i>aureus</i> spleen concentrations 8 and 24 hours after bacteria instillation. Spleen bacterial burden according to the experimental group in either spontaneously breathing (SB + <i>S</i>. <i>aureus</i>) or mechanically ventilated (MV + <i>S</i>. <i>aureus</i>) animals with <i>Staphylococcus aureus</i> pneumonia (n = 4 and 5, respectively*). Interestingly, MV appears to promote early pulmonary-to-systemic translocation during <i>S</i>. <i>aureus</i> pneumonia, as indicated by the quantitative spleen cultures, as an indirect marker of bacteraemia, which were positive only in ventilated animals after 8 hours, even though there was no longer any difference after 24 hours. *spleen was lost in 1 animal from each group. Lung <i>S</i>. <i>aureus</i> concentrations SB versus (vs) MV 8 hours <i>p</i> = 0.050; Mann-Whitney U test, two-tailed. Lung <i>S</i>. <i>aureus</i> concentrations SB vs MV 24 hours <i>p</i> = 0.007; Mann-Whitney U test, two-tailed. Spleen <i>S</i>. <i>aureus</i> concentrations SB vs MV 8 hours <i>p</i> = 0.430; Mann-Whitney U test, two-tailed. Spleen <i>S</i>. <i>aureus</i> concentrations SB vs MV 24 hours <i>p</i> = 0.110; Mann-Whitney U test, two-tailed.</p