Abstract
Background: Time to Positivity (TTP) of blood cultures is defined as the time elapsed between the start of incubation and the automated alert signal indicating growth in the culture bottle. This study evaluates the TTP of blood cultures in patients with Staphylococcus aureus Bacteremia (SAB) and assesses the relationship between TTP and mortality, Methods: We performed a retrospective study involving adults who had SAB between May 2007 and May 2010 in a tertiary hospital. TTP was defined as the time between onset of incubation and growth detection using an automated blood culture system. Results: A total of 167 SAB were evaluated. Patient’s median age was 72 years (range, 18-95 years). The median TTP was 13.6 h (range, 3.6-95.2 h). Attributable mortality rate (27.5%) was not related to the TTP (P=0.558) nor to the comorbidities. Age >60 years was the only independent predictor of attributable mortality (P 11.3 h had a negative predictive value of 96.4% for endocarditis. TTP was not related to methicillin susceptibility nor resistance of Staphylococcus aureus (P=0.934). Conclusion: In our elderly population, shorter TTP was significantly associated with a central source of infection and a persistent SAB. In addition for the first time, community-acquired SAB was associated with a shorter TTP. TTP may contribute to a better management of SAB by facilitating clinical decisions, especially in endocarditis
Highlights
Time to Positivity (TTP) of blood cultures is defined as the time elapsed between the start of incubation and the automated alert signal indicating growth in the culture bottle
Differential TTP is used for the diagnosis of catheterrelated bacteremia [2,4,5,6,7] and TTP is used for predicting the presence of Staphylococcus spp. bacteria in blood culture [8,9]
Studies showed that a TTP ≤ 14 h was correlated to attributable mortality in bacteremia varying from 11.9% to 18% [3,11,12]
Summary
TTP is an indirect marker of the bacterial load and is associated with a higher morbidity and mortality [3]. Time to Positivity (TTP) of blood cultures is defined as the time elapsed between the start of incubation and the automated alert signal indicating growth in the culture bottle. This study evaluates the TTP of blood cultures in patients with Staphylococcus aureus Bacteremia (SAB) and assesses the relationship between TTP and mortality, Methods: We performed a retrospective study involving adults who had SAB between May 2007 and May 2010 in a tertiary hospital. TTP was defined as the time between onset of incubation and growth detection using an automated blood culture system
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