Related Experiment Video
Updated: May 8, 2026

Preparation of a Blood Culture Pellet for Rapid Bacterial Identification and Antibiotic Susceptibility Testing
Published on: October 15, 2014
Differential time to positivity is not predictive for central line-related Staphylococcus aureus bloodstream
Achim J Kaasch1, Siegbert Rieg, Martin Hellmich
1Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Goldenfelsstraße 19-21, 50935 Cologne, Germany.
Objectives:
Many physicians rely on differential time to positivity (DTP) when diagnosing catheter-related bloodstream infection (CRBSI). We evaluated whether DTP from routine blood cultures can predict catheter-related Staphylococcus aureus bloodstream infection.
Methods And Patients:
From 2006 to 2011 adult patients with monomicrobial S. aureus bloodstream infection and matched pairs of central and peripheral blood cultures were prospectively followed. CRBSI was defined by the absence of other infective foci and recovery of S. aureus from the catheter tip or catheter exit-site, or local signs of infection at the catheter exit site. A DTP of more than two hours (cut-off) was used to define test positivity.
Results:
CRBSI was present in 30 (34%, prevalence) of 87 patients. In 24 (28%) patients a DTP of more than two hours was measured: eleven patients had CRBSI, ten deep-seated infections, and in three patients an infective focus was not identified. DTP showed a positive predictive value of 0.46 [95% confidence interval (CI) 0.28 to 0.65], and a negative predictive value of 0.70 [95% CI 0.58 to 0.80].
Conclusion:
The low test performance suggests that DTP is not useful in diagnosing CRBSI in routinely obtained blood cultures. Therefore, physicians should not solely rely on DTP and rather promote catheter removal and culture.
More Related Videos
09:07Direct Microbial Identification using An Automated Microbial Identification System to Facilitate the EUCAST RAST Method Without Mass Spectrometry
Published on: May 24, 2024
08:30One-day Workflow Scheme for Bacterial Pathogen Detection and Antimicrobial Resistance Testing from Blood Cultures
Published on: July 9, 2012
Related Concept Videos
Differential Staining Technique
Clinical Significance of Antibiotic Resistance
Factors Affecting the Risk of Infection
The integrity and count of the white blood cells help the body resist pathogens and fight infection. When impaired, it reduces the body's resistance to pathogens. The acidic pH levels of the gastrointestinal, genitourinary tracts, and skin create...
Automated Microbial Diagnostics
Urine Studies II: Urine Culture and Sensitivity Test
Sensitivity, Specificity, and Predicted Value
Sensitivity is the...