Association between time to gram stain positivity and true bacteremia in pediatric emergency department patients
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Published on: October 15, 2014
Brandon Noyon1, Alino Demean Loghin1, Charlotte Grandjean-Blanchet2
1Faculty of medicine, Université de Montréal, Montréal, QC, Canada.
Insights
Time to Gram stain positivity in blood cultures can help differentiate true bacteremia from contaminants in febrile children. Faster positivity times strongly indicate true bacteremia, aiding clinical decisions.
Area of Science:
- Pediatric Infectious Diseases
- Clinical Microbiology
- Emergency Medicine
Background:
- Febrile children with positive blood cultures pose a diagnostic challenge due to the risk of true bacteremia versus contaminants.
- Accurate differentiation is crucial for timely and appropriate patient management.
Purpose of the Study:
- To investigate the association between the time to Gram stain positivity and the likelihood of true bacteremia in pediatric patients with positive blood cultures.
- To provide data to aid emergency department (ED) decision-making regarding positive blood cultures.
Main Methods:
- Secondary analysis of a retrospective cohort study (2018-2024) of children with positive blood cultures in a tertiary pediatric ED.
- True bacteremia was defined using a two-step approach: bacterial identification and clinical outcome assessment.
- Correlation between time to Gram stain positivity and bacteremia likelihood was assessed by comparing median times and calculating probabilities.
Main Results:
- Median time to Gram stain positivity was significantly shorter for true bacteremia (14 hours) compared to contaminants (19 hours).
- Probability of bacteremia ranged from 94% for positivity <10 hours to 19% for positivity >48 hours.
- Approximately 90% of true bacteremia cases showed positivity within 24 hours.
Conclusions:
- Time to Gram stain positivity is a reliable indicator for distinguishing true bacteremia from contaminants in pediatric blood cultures.
- This finding can help optimize patient management, potentially reducing unnecessary interventions and hospital stays.
Study Objective:
Febrile children with positive blood cultures require prompt intervention due to the risk of true bacteremia. However, approximately half of the pediatric positive blood cultures are contaminants. To aid decision-making, we investigated the relationship between time to Gram stain positivity and the likelihood of true bacteremia among children with positive blood cultures in the emergency department (ED).
Methods:
This was a secondary analysis of a retrospective cohort study using data from 2018 to 2024. Participants included all children with positive blood cultures from a tertiary pediatric ED. True bacteremia was defined using a standardized two-step approach, involving identification of the bacteria responsible and assessing clinical outcomes by two independent examiners. We investigated the correlation between time to Gram stain positivity and the likelihood of true bacteremia by comparing median time to positivity for both groups and reporting the probability of bacteremia based on timing.
Results:
Of the 487,222 children presenting to the ED, 746 had positive blood cultures out of 38,541 blood cultures performed, of which 368 were classified as true bacteremia. Median time to Gram stain positivity was significantly shorter for true bacteremia (14 h) compared to contaminants (19 h) (difference: 5 h; 95 % CI: 4-6 h). The probability of bacteremia varied from 94 % for cultures positive in less than 10 h to 19 % for cultures positive after 48 h. Nearly 90 % of true bacteremia cases tested positive within 24 h.
Conclusion:
Time to Gram stain positivity is a strong indicator for distinguishing true bacteremia from contaminants, potentially optimizing patient management and reducing unnecessary hospital stays.
