Time to positivity (TTP) of blood cultures in patients with bacteraemia is considered to be a predictor of outcome for some bacterial species. Two hundred and thirty-one patients with Klebsiella pneumoniae monomicrobial bacteraemia at a hospital from 1 January to 31 December 2007 were prospectively enrolled. TTP <7 h (46 patients, 19.9%) was associated with a higher Pittsburg bacteraemia score (6.2 +/- 5.5 vs. 3.7 +/- 4.3, p 0.002), fewer non-fatal diseases by the McCabe classification (39.1% vs. 64.9%, p 0.002), a higher percentage of patients with liver cirrhosis, active malignancy, and chemotherapy within 3 months (28.3% vs. 11.9%, p 0.007; 28.3% vs. 14.6%, p 0.031; 23.9% vs. 5.4%, p <0.001), more primary bacteraemia (45.7% vs. 22.2%, p 0.002), and a higher 30-day mortality rate (47.8% vs. 21.1%, p <0.001). Risk factors for 30-day mortality in the univariate analysis included higher Pittsburg bacteraemia score (5.8 +/- 5.3 vs. 3.7 +/- 4.3, p 0.002), primary bacteraemia (41.0% vs. 21.8%, p 0.004), TTP <7 h (36.1% vs. 14.1%, p <0.001), and the presence of active malignancy (29.5% vs. 12.9%, p 0.004). In the multivariate analysis, higher Pittsburg bacteraemia score (OR 1.07; 95% CI 1.01-1.14), TTP <7 h (OR 2.46; 95% CI 1.20-5.05) and active malignancy (OR 2.21; 95% CI 1.03-4.73) were the significant factors associated with 30-day mortality. In the Kaplan-Meier survival curve, short TTP was significantly associated with mortality at all time-points after admission. TTP of blood cultures, interpreted with a cut-off point of <7 h, in patients with K. pneumoniae bacteraemia can provide useful prognostic information.

Leukoreduction in blood units could prevent patients undergoing transfusions from transfusion-associated adverse reactions (TAARs) such as febrile nonhemolytic transfusion reactions (FNHTRs). However, the effect of prestorage and poststorage leukoreduction on TAARs and its underlying mechanisms in stored blood components remains to be determined. Therefore, we investigated the impact of prestorage leukocyte-reduced (pre-LR) and poststorage leukocyte-reduced (post-LR) blood products, including red blood cells (RBCs) and apheresis platelets (PHs), on the incidence of FNHTRs and other TAARs in patients who received transfusions from 2009 to 2014 in a tertiary care center. We also investigated the difference of leukocyte-related bioactive mediators between pre- and post-LR blood components. The results indicated that prevalence of TAARs was significantly reduced in the transfusions of pre-LR blood components. Particularly, the prevalence of FNHTRs was significantly reduced in the pre-LR RBC transfusions and the prevalence of allergy reactions was markedly reduced in the pre-LR PH transfusions. Furthermore, in vitro evaluation of cytokines in the pre- and post-LR blood components revealed that IL-1β, IL-8 and RANTES levels were significantly elevated in the post-LR RBCs during the storage. In contrast, IL-1β, IL-6 and IL-8 levels were significantly elevated in the post-LR PHs during the storage. These findings suggested that prestorage leukoreduction had a diminishing effect on the development of TAARs, which could be associated with less accumulation of cytokines in the stored blood components.