Correlation between time to positivity of blood cultures with clinical presentation and outcomes in patients with Klebsiella pneumoniae bacteraemia: prospective cohort study.

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.