Differential host response to Methicillin‐resistant Staphylococcus aureus and Pseudomonas aeruginosa

Abstract

Despite the outstanding achievement in treatment of sepsis, the mortality rate of septic patients is high. The objective of the study was to describe differential host response to different infectious agents using our well‐established ovine sepsis model.MethodSheep were given the injury via tracheostomy under anesthesia. Study groups: 1) sham, (no injury), n=6; 2) Smoke (Smoke inhalation) n=6; 3) PS (smoke inhalation & Ps. aeruginosa (1011CFU) instilled into the lungs, n=6; 4) MRSA (smoke inhalation & MRSA (1011CFU) instilled into the lungs, n=6. After injury, sheep were awakened, maintained on mechanical ventilation, and fluid resuscitated for 24 h.Results:Mean arterial pressure was similarly depleted in MRSA and PS groups. The severity of lung injury was more pronounced in PS group, which was associated with higher expression of lung IL‐1, 6, and 8. MRSA group had 2‐fold higher fluid retention associated with significantly higher nitric oxide (NO) production and vascular endothelial growth factor (VEGF). The lung tissue arginase level and IL‐13 was higher in PS group.Conclusion:Excess IL‐13 leading to higher arginase activity in PS may result in lesser production of NO. The severe vascular leak in MRSA group may be due to excess NO and VEGF. Differential responses to different pathogenic agents require more focused treatment approach considering the nature of infectious agents and specific host response to it