The chemokine CCL4 can be an active player in the inflammatory response and chemotaxis during sepsis (5, 49, 50). and 38 (47.5%) patients showed positive and negative blood cultures, respectively. There were significant differences in plasma levels of six soluble mediators between the two bacteremia and non-bacteremia groups, using MannCWhitney test (test for continuous variables and the 2 2 test for categorical variables (33). For a more comprehensive analysis, we selected those soluble mediators showing a significant difference and fitted a logistic regression model with the groups as outcomes and the mediators as predictors adjusted according to both age and organ failure (34). We estimated both a univariate model for each of the selected mediators and a fully adjusted model that included all selected predictors. Additionally, we performed unsupervised hierarchical clustering analyzes with complete linkage and Euclidean distance (27, 35). For both the logistic regression and cluster analyzes, the mediator values were log10- and testtest was used for the comparisons, em p /em ? ?0.05 were regarded as significant and em p /em ? ?0.0014 were also significant after Bonferroni correction. Univariate logistic regression showed significant results for all of these six soluble mediators (Table ?(Table2).2). In a multivariate logistic regression model that included all six soluble mediators, VCAM-1 still showed statistically significant differences in plasma levels between patients with, compared with those without bacteremia, whereas age and organ failure did not impact the logistic SMER18 regression model, and were not included in the final model. The 10 soluble mediators showing statistically significant differences in plasma levels only before Bonferroni correction were also heterogeneous in biological function and included; the anti-inflammatory mediators IL-1ra, IL-10, and HGF; the pro-inflammatory chemokines CCL2, CCL5, CXCL8, and CXCL11, MMP-8; and the protease inhibitors TIMP-2 and TIMP-4 (Table ?(Table2;2; Physique ?Physique22). The Systemic Soluble Mediator Profile Shows Only Minor Differences Between Patients With Gram-Positive and Those With Gram-Negative Bacterial Infections We compared the soluble mediator levels between patients with documented Gram-positive bacterial infections and those with Gram-negative bacterial infections, which also included patients with and without bacteremia. Results showed only minor differences in plasma profiles between the Gram-positive and Gram-negative bacterial infection groups. We observed significant differences only for CCL4 ( em p /em ?=?0.0057), CXCL5 ( em p /em ?=?0.0452), CXCL10 ( em p /em ?=?0.0393), and leptin ( em p /em ?=?0.0150), with higher levels of CCL4 and CXCL5 in the Gram-negative group, and with higher levels of CXCL10 and leptin in the Gram-positive group. However, SMER18 these differences were not significant after Bonferroni correction. Identification of a Patient Subset With a Low Frequency of Bacteremia by Unsupervised SMER18 Hierarchical Clustering of All Mediators We performed unsupervised hierarchical clustering including all 35 soluble mediators and all 80 patients with sepsis with an identified bacterial cause. This was performed to determine the covariation of both patients and soluble mediators (Physique ?(Figure33). Open in a separate window Physique 3 Unsupervised hierarchical clustering analysis of plasma levels for 35 detectable mediators, and an analysis including all 80 patients. The concentrations were log10 converted and em Z /em -transformed standardized before unsupervised hierarchical clustering. Euclidian correlation test with complete linkage were used for the clustering analysis. The heat-map displays a small square for each mediator for each patient, and each squares colors displays its concentration compared with mean and corrected for SD. The mediators are clustered horizontally and a tree is usually formed at the top of the physique that display the covariation of different mediators, and to the left a tree is usually formed where patients with comparable mediator covariation cluster together. To the right, we Cd24a have added clinical information. We see that most mediators cluster close to (i.e., have a similar variation as) biologically related mediators and most of the mediators that differ between the patients are grouped in or between cluster A (red) and B (blue). The patients are clustered vertically and form three main clusters, 1, 2, and 3. The patients with bacteremia are marked in red in the right column. Cluster 3 with the.