Time-to-positivity of blood culture: An independent prognostic factor of monomicrobial Pseudomonas aeruginosa bacteremia

Abstract

Background/purpose: Pseudomonas aeruginosa bacteremia is an important cause of nosocomial infections with high morbidity and mortality. Time-to-positivity (TTP) of blood cultures is considered to be a predictor of the clinical outcome for bacteremia. The aim of the study is to investigate the relationship between TTP and clinical outcomes in patients with monomicrobial P. aeruginosa bacteremia.

Methods: From January 2013 to June 2014, a retrospective cohort study was conducted in a 1200-bed tertiary care hospital. The cases of monomicrobial P. aeruginosa bacteremia were studied. TTP and clinical parameters were determined and analyzed.

Results: In 139 cases of P. aeruginosa bacteremia, TTP ≤ 13 hours was associated with higher Pitt bacteremia scores (5.3 ± 4.2 vs. 2.3 ± 2.8, p < 0.001), severe sepsis (66.1% vs. 35.0%, p < 0.001), higher 30-day mortality rate (54.2% vs. 15.0%, p < 0.001), longer hospitalization in the survivors (25.6 ± 48.5 days vs. 16.3 ± 15.3 days, p = 0.16), and more admission to intensive care unit (27.2% vs. 16.3%, p = 0.14). Risk factors for 30-day mortality in the univariate analysis included corticosteroid exposure, primary bacteremia, concurrent pneumonia, a high Pitt bacteremia score, severe sepsis, and TTP ≤ 13 hours. In the multivariate analysis, primary bacteremia, a pulmonary origin of bacteremia, severe sepsis, and TTP ≤ 13 hours were independent risk factors for 30-day mortality.

Conclusion: In cases of monomicrobial P. aeruginosa bacteremia, a short TTP (≤ 13 hours) provides prognostic information, in addition to clinical parameters.

Keywords: Pseudomonas aeruginosa; bacteremia; time-to-positivity.