Molecular inflammatory responses measured in blood of patients with severe community-acquired pneumonia

Abstract

In order to analyze the characteristics of the inflammatory response occurring in blood during pneumonia, we studied 38 patients with severe community-acquired pneumonia. Venous and arterial blood samples were collected at study entry and on days 1, 2, 3, 5, and 7 after inclusion. The concentrations of proinflammatory (tumor necrosis factor alpha [TNF-alpha], interleukin 1beta [IL-1beta], IL-6, and IL-8) and anti-inflammatory (IL-10) cytokines were determined in order to detect differences related to the origin of the sample, the causative organism, the clinical variables, and the final outcome of the episode. Legionella pneumonia infections showed higher concentrations of TNF-alpha, IL-6, IL-8, and IL-10. After 24 h, plasma IL-6, IL-8, and IL-10 concentrations in pneumococcal episodes increased, whereas in the same time interval, cytokine concentrations in Legionella episodes markedly decreased. The characteristics of the inflammatory response in bacteremic pneumococcal episodes were different from those in nonbacteremic episodes, as indicated by the higher plasma cytokine concentrations in the former group. Finally, our analysis of cytokine concentrations with regard to the outcome--in terms of the need for intensive care unit admittance and/or mechanical ventilation as well as mortality--suggests that there is a direct relationship between the intensity of the inflammatory response measured in blood and the severity of the episode.

FIG. 1.

Pneumococcal and Legionella pneumonias. Comparative changes in the absolute daily plasma IL-6 and IL-10 concentrations and their variations over time in relation to the initial values are shown. An asterisk indicates a statistically significant difference in the comparisons of groups, as determined by the Mann-Whitney U test. A dagger indicates a statistically significant difference in relation to basal values, as determined by the Kruskal-Wallis one-way analysis of variance nonparametric test. For P values, see the text. The pairs of small numbers appearing just below the horizontal axis represent the numbers of observations in the subgroups of patients at different time intervals from admission. Min-max, minimum-maximum.

FIG. 2.

Bacteremic and nonbacteremic pneumococcal pneumonias. Daily and time course comparisons of plasma IL-6 and IL-10 concentrations are shown. An asterisk indicates a statistically significant difference in the comparisons of groups, as determined by the Mann-Whitney U test. A dagger indicates a statistically significant difference in relation to basal values, as determined by the Kruskal-Wallis one-way analysis of variance nonparametric test. For P values, see the text. The pairs of small numbers appearing just below the horizontal axis represent the numbers of observations in the subgroups of patients at different time intervals from admission. Min-max, minimum-maximum.

FIG. 3.

Survivors and nonsurvivors. Daily changes as well as time course changes in plasma IL-6 and IL-10 concentrations are shown. An asterisk indicates a statistically significant difference in the comparisons of groups, as determined by the Kruskal-Wallis one-way analysis of variance nonparametric test. A dagger indicates a statistically significant difference in relation to basal values, as determined by the Kruskal-Wallis one-way analysis of variance nonparametric test. For P values, see the text. The pairs of small numbers appearing just below the horizontal axis represent the numbers of observations in the subgroups of patients at different time intervals from admission. Min-max, minimum-maximum.