Clinical impact of time-to-positivity of blood cultures on mortality in patients with Pseudomonas aeruginosa bacteremia

Objectives: To investigate the impact of the time-to-positivity of blood cultures (TTP) on 30-day mortality in patients with Pseudomonas aeruginosa bacteremia. Methods: All nonduplicated episodes of P. aeruginosa monomicrobial bacteremia in adult patients from January 2013 to February 2020 were analysed. Epidemiological and clinical data were collected. TTP of blood cultures for P. aeruginosa isolates was automatically recorded. Multivariate analysis identified factors predicting 30-day overall mortality. Results: A total of 328 patients were identified. The median TTP for P. aeruginosa isolates was 15 h (interquartile range [IQR] 12-18 h). All multidrug-resistant and extensively drug-resistant (MDR/XDR) episodes were positive within the first 36 h. The 30-day mortality rate was 32.3%. The best cut-off value of the TTP for predicting mortality was 16 h (area under the receiver operating characteristic curve 0.62, 95% confidence interval [CI] 0.56-0.67, P = 0.001). The 30-day mortality rate was significantly higher in the TTP <= 16 h group (41.0% vs. 19.5%, P < 0.001). In a multivariate analysis, severe neutropenia (adjusted odds ratio [aOR] 2.67, 95% CI 1.4-5.09, P = 0.002), septic shock (aOR 3.21, 95% CI 1.57-5.89, P < 0.001), respiratory source (aOR 4.37, 95% CI 2.24-8.52, P < 0.001), nosocomial acquisition (aOR 1.99, 95% CI 1.06-3.71, P = 0.030), TTP <= 16 h (aOR 2.27, 95% CI 2.12-4.25, P = 0.010), and MDR/XDR phenotype (aOR 2.54, 95% CI 1.38-4.67, P = 0.002) were independently associated with 30-day mortality. Conclusions: A short TTP (<= 16 h) was independently associated with increased 30-day mortality. After local validation, this routinely available microbiological parameter might be useful for guiding empirical antipseudomonal therapies and supporting the close monitoring of patients with P. aeruginosa bacteremia. (C) 2022 The Author(s). Published by Elsevier Ltd on behalf of International Society for Antimicrobial Chemotherapy.