interleukin-8 and Pneumonia--Staphylococcal

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)-αserum 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-α: 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.

Topics: Animals; Interleukin-8; Pneumonia, Staphylococcal; Pneumonia, Ventilator-Associated; Rabbits; Respiration, Artificial; Staphylococcus aureus; Toll-Like Receptor 2; Tumor Necrosis Factor-alpha

Community-acquired Staphylococcus aureus necrotizing pneumonia is a life-threatening disease. Panton Valentine Leukocidin (PVL) has been associated with necrotizing pneumonia. PVL triggers inflammasome activation in human macrophages leading to IL-1β release. IL-1β activates lung epithelial cells to release IL-8. This study aimed to assess the relevance of this inflammatory cascade in vivo and to test the potential of an IL-1 receptor antagonist (IL-1Ra/Kineret) to decrease inflammation-mediated lung injury.. We used the sequential instillation of Heat-killed S. aureus and PVL or S. aureus infection to trigger necrotizing pneumonia in rabbits. In these models, we investigated inflammation in the presence or absence of IL-1Ra/Kineret.. We demonstrated that the presence of PVL was associated with IL-1β and IL-8 release in the lung. During PVL-mediated sterile pneumonia, Kineret/IL-1Ra reduced IL-8 production indicating the relevance of the PVL/IL-1/IL-8 cascade in vivo and the potential of Kineret/IL-1Ra to reduce lung inflammation. However, Kineret/IL-1Ra was ineffective in blocking IL-8 production during infection with S. aureus. Furthermore, treatment with Kineret increased the bacterial burden in the lung.. Our data demonstrate PVL-dependent inflammasome activation during S.aureus pneumonia, indicate that IL-1 signaling controls bacterial burden in the lung and suggest that therapy aimed at targeting this pathway might be deleterious during pneumonia.

Topics: Animals; Bacterial Toxins; Exotoxins; Inflammasomes; Interleukin 1 Receptor Antagonist Protein; Interleukin-1beta; Interleukin-8; Leukocidins; Macrophages; Pneumonia, Staphylococcal; Rabbits

 Linezolid is recommended for treatment of pneumonia and other invasive infections caused by methicillin-resistant Staphylococcus aureus (MRSA). The premise underlying this recommendation is that linezolid inhibits in vivo production of potent staphylococcal exotoxins, including Panton-Valentine leukocidin (PVL) and α-hemolysin (Hla), although supporting evidence is lacking..  A rabbit model of necrotizing pneumonia using MRSA clone USA300 was used to compare therapeutic effects of linezolid (50 mg/kg 3 times/day) and vancomycin (30 mg/kg 2 times/day) administered 1.5, 4, and 9 hours after infection on host survival outcomes and in vivo bacterial toxin production..  Mortality rates were 100% for untreated rabbits and 83%-100% for vancomycin-treated rabbits. In contrast, mortality rates were 25%, 50%, and 100% for rabbits treated with linezolid 1.5, 4, and 9 hours after infection, respectively. Compared with untreated and vancomycin-treated rabbits, improved survival of rabbits treated 1.5 hours after infection with linezolid was associated with a significant decrease in bacterial counts, suppressed bacterial production of PVL and Hla, and reduced production of the neutrophil-chemoattractant interleukin 8 in the lungs..  Across the study interval, only early treatment with linezolid resulted in significant suppression of exotoxin synthesis and improved survival outcomes in a rabbit model of MRSA necrotizing pneumonia.

Topics: Acetamides; Animals; Anti-Bacterial Agents; Bacterial Load; Bacterial Toxins; Chemokine CCL2; Disease Models, Animal; Exotoxins; Hemolysin Proteins; Interleukin-8; Leukocidins; Linezolid; Lung; Methicillin-Resistant Staphylococcus aureus; Oxazolidinones; Pneumonia, Staphylococcal; Rabbits; Vancomycin

To assess the efficacy of linezolid compared with vancomycin in an experimental model of pneumonia induced by methicillin-resistant Staphylococcus aureus (MRSA) in ventilated pigs.. Forty pigs (30 kg) were intubated and challenged via bronchoscopy with a suspension of 106 colony forming units of MRSA into every lobe. Afterwards, pigs were ventilated up to 96 hours. Twelve hours after bacterial inoculation, the animals were randomized into 4 groups of treatment: group 1, control; group 2, vancomycin twice daily; group 3, continuous infusion of vancomycin; and group 4, linezolid. Clinical and laboratory parameters were monitored throughout the study. Bacterial cultures of bronchoalveolar lavage fluid and lung tissue samples were performed at the end of the study. Measurements of histopathology derangements of lung samples and studies of intrapulmonary drug penetration were performed.. A total of 34 animals completed the study. No differences in clinical and laboratory parameters were observed. The percentage of bronchoalveolar lavage fluid and lung tissue samples with positive cultures for MRSA in controls and groups 2, 3, and 4 was respectively 75%, 11%, 11%, and 0% (p < .01); 52%, 9%, 24%, and 2.5% (p < .01). Histopathology studies demonstrated signs of pneumonia in 95%, 69%, 58%, and 57% and signs of severe pneumonia in 48%, 29%, 22%, and 0% of controls and groups 2, 3, and 4, respectively (p < .01). In addition, pharmacokinetics/pharmacodynamics profile in serum and lung tissue showed better results for linezolid compared with both vancomycin treatments.. In this animal model of MRSA pneumonia, linezolid showed a better efficacy than vancomycin showed because of a better pharmacokinetics/pharmacodynamics index.

Topics: Acetamides; Animals; Anti-Bacterial Agents; Bronchoalveolar Lavage Fluid; Disease Models, Animal; Interleukin-6; Interleukin-8; Linezolid; Lung; Methicillin-Resistant Staphylococcus aureus; Oxazolidinones; Pneumonia, Staphylococcal; Pneumonia, Ventilator-Associated; Respiration, Artificial; Swine; Tumor Necrosis Factor-alpha; Vancomycin

Staphylococcus aureus is a major human pathogen that is associated with diverse types of local and systemic infection characterized by inflammation dominated by polymorphonuclear leukocytes. Staphylococci frequently cause pneumonia, and these clinical isolates often have increased expression of protein A, suggesting that this protein may have a role in virulence. Here we show that TNFR1, a receptor for tumor-necrosis factor-alpha (TNF-alpha) that is widely distributed on the airway epithelium, is a receptor for protein A. We also show that the protein A-TNFR1 signaling pathway has a central role in the pathogenesis of staphylococcal pneumonia.

Topics: Animals; Blotting, Western; Cell Line; Disease Models, Animal; Enzyme-Linked Immunosorbent Assay; Flow Cytometry; Humans; Immunohistochemistry; Interleukin-8; Lung; Mice; Mice, Inbred C57BL; Microscopy, Confocal; Neutrophils; Pneumonia, Staphylococcal; Receptors, Tumor Necrosis Factor; Respiratory Mucosa; Signal Transduction; Staphylococcal Protein A; Staphylococcus aureus

Staphylococcus aureus strains lacking agr- and sarA-dependent gene products or specific MSCRAMM (microbial surface components recognizing adhesive matrix molecules) adhesins were compared for the ability to activate inflammatory responses in the lung. The mutants were evaluated for virulence in a mouse model of pneumonia and by quantifying their ability to stimulate interleukin-8 (IL-8) and granulocyte-macrophage colony-stimulating factor (GM-CSF) expression in respiratory epithelial cells. In a neonatal mouse, only strains with intact agr and sarA loci were consistently associated with invasive, fatal pulmonary infection (P < 0.001) and sarA was specifically required to cause bacteremia (P < 0.001). The agr and/or sarA mutants were, nonetheless, fully capable of producing pneumonia and were as proficient as the wild-type strain in stimulating epithelial IL-8 expression, a polymorphonuclear leukocyte chemokine, in airway cells. In contrast, agr and especially sarA mutants induced less epithelial GM-CSF expression, and MSCRAMM mutants lacking fibronectin binding proteins or clumping factor A, a ligand for fibrinogen, were unable to stimulate epithelial GM-CSF production. The ability to induce IL-8 expression was independent of the adherence properties of intact bacteria, indicating that shed and/or secreted bacterial components activate epithelial responses. While conserved staphylococcal components such as peptidoglycan are sufficient to evoke inflammation and cause pneumonia, the agr and sarA loci of S. aureus are critical for the coordination of invasive infection of the lungs.

Topics: Animals; Bacterial Adhesion; Bacterial Proteins; Cell Line, Transformed; Coagulase; Gene Expression; Granulocyte Colony-Stimulating Factor; Granulocyte-Macrophage Colony-Stimulating Factor; Humans; Interleukin-8; Lipopolysaccharides; Mice; Mice, Inbred BALB C; Mutation; Pneumonia, Staphylococcal; Staphylococcal Infections; Staphylococcus aureus; Teichoic Acids; Trans-Activators; Transcription Factors; Virulence