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Volume 50, Number 4, August 2017

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

Poh-Chang Tang, Ching-Chi Lee, Chia-Wen Li, Ming-Chi Li, Wen-Chien Ko, Nan-Yao Lee


Corresponding author:

Wen-Chien Ko, Corresponding authors. Department of Internal Medicine, National Cheng Kung University Hospital, Number 138, Sheng Li Road, 704, Tainan, Taiwan. 


Background and 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. 



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.




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.




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


Key words:

bacteremia, Pseudomonas aeruginosa, time-to-positivity