Secondary Lung Infection Research Articles

IL-12 Administered During Chlamydia psittaci Lung Infection in Mice Confers Immediate and Long-Term Protection and Reduces Macrophage Inflammatory Protein-2 Level and Neutrophil Infiltration in Lung Tissue

Abstract Protection against infections with the intracellular bacterium Chlamydia spp. requires Th1-polarized CD4+ T cell immunity. In BALB/c mouse lung infections, immediate innate and nascent Chlamydia-specific immune responses following intranasal inoculation of Chlamydia psittaci strain B577 were modulated by 7-day i.p. administration of murine rIL-12, the initiation cytokine for Th1 immunity. Treatment with IL-12 reduced the severity of chlamydial pneumonia, abolished mortality (37.5% in untreated mice), and significantly reduced numbers of chlamydial organisms in lungs. On day 4 after inoculation, the neutrophil:macrophage ratio in bronchointerstitial pneumonias was 1.96 in untreated mice and 0.51 in IL-12-treated mice. This immediate, IL-12-mediated shift in innate inflammatory phenotype was correlated with a significant reduction of lung concentrations of the neutrophil chemoattractant macrophage inflammatory protein (MIP)-2 (putative murine homologue of human IL-8), monocyte chemotactic protein-1, and TNF-α; and a reduction in MIP-1α and IFN-γ, at high-dose infection only, and IL-12-independent IL-10 levels. Chlamydia-specific Ab titers and Ig isotype ratios indicated an IL-12-dependent Th1 shift. Recall responses of IL-12-primed mice to secondary chlamydial lung infection eliminated chlamydiae more effectively and generated a lung cytokine profile conducive to perpetuation of the Th1 memory population. These data support the hypothesis that genetic differences in endogenous IL-12 production and response pathways could determine disease outcomes characterized by poor chlamydial clearance and a purulent inflammatory infiltrate vs effective elimination of chlamydiae in a macrophage-dominated response.

Post-Infectious ARDS: Mechanisms of Lung Injury and Repair

Lung infections are considered the most common causes of ARDS. Additionally, superimposed secondary lung infections may occur in the setting of ARDS and further aggravate lung damage. Substances released by neutrophils are the major mediators of lung injury, although other factors, such as endotoxin, exotoxins, macrophages, and immune mechanisms, are significant contributors. Neutrophil-induced lung injury results from the production of oxygen radicals, the release of products of arachidonate metabolism, and the activation of lysosomal enzymes. The development of ARDS is associated with high mortality. Although a large proportion of survivors eventually recover adequate lung function, some patients progress to severe fibrosis. Experimental evidence suggests that the development of fibrosis results from increased synthesis of ECM components by lung fibroblasts. Fibroblast synthesis of ECM components is normally influenced by alveolar cells, by circulating growth factors, by the external milieu, and by the extent of gene expression of the specific ECM components. These factors undergo significant alterations during the evolution of experimental lung fibrosis. Growth factors are more abundant, alveolar cells are activated, and gene expression is enhanced. These factors, which play a crucial role in promoting experimental lung fibrosis, are likely to be involved in the pathogenesis of fibrosis in post-infectious ARDS.

Fresh water drowning: a case report

A case of near-drowning in fresh water with initial neurological malfunction and severe changes in blood gases and pH is reported, and treatment of the patient discussed. Pulmonary oedema was initially predominant, and it was successfully treated by mechanical ventilation with continuous positive pressure respiration. A secondary lung infection with Pseudomonas responded to Carbencillin (20 g/day), Probenecid (1·5 g/day) and Gentamycin (180 mg/day) administered for 20 days. Six months after the patient was discharged, his lung function was normal. The importance of treating near-drowning patients in an intensive care unit is emphasized.