Time to Positivity of Blood Cultures in Infants 0 to 90 days old: Is 36 hours enough?
CPS ePoster Library. Lefebvre C. 06/25/15; 99078; 15
Claire Lefebvre
Claire Lefebvre
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Abstract
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Purpose

New advances in blood culture incubation systems – continuous monitoring blood culture systems (CMBCS) – now allow for more precise determination of blood cultures’ “time to positivity” (TTP). We aimed to determine whether a period of 36 hours (instead of the traditional 48 hours) was sufficient to detect all blood cultures positive for pathogenic bacteria in infants between the ages of 0 and 90 days presenting to the emergency department (ED) of an urban tertiary care pediatric center and undergoing a septic workup.

Methods

We performed a retrospective study of all positive blood cultures collected in the ED from infants 0 to 90 days old, over a 5-year time period (from March 13th 2008 to July 29th 2013). In our institution, blood culture bottles are received and incubated 24 hours a day, 7 days a week in a CMBCS (VersaTREK; Thermo Scientific). The TTP was calculated using the time interval from blood culture registration into the system to the time of gram stain, obtained from the microbiology Laboratory Information System (SoftMic, Medisolution). Medical charts were reviewed using a standardised data collection form to obtain relevant clinical information. With the help of a microbiologist-infectious disease specialist and a pediatrician, cultures were further divided into pathogenic or contaminant, based on organism and clinical presentation.

Results

Three thousand five hundred fifty-nine (3,559) blood cultures were collected from infants 0 to 90 days old in the ED during the study period. Of these, 98 (2.8%) were positive, collected from 96 infants (64 boys; 34 girls) with a mean age of 40.4 days. Among these positive cultures, 52 (53.1%) were deemed pathogenic and 46 (46.9%) were deemed contaminant, for a true prevalence of bacteremia of 1.5%. At 24, 36, 48, and 50 hours of incubation, 87.8% (86/98), 96.9% (95/98), 99% (97/ 98), and 100% (98/98) of all cultures were positive, respectively. If we consider only those organisms deemed pathogenic, at 24 and 36 hours respectively, 96.1% (50/52) and 100% (52/52) were positive. Mean TTP for pathogens and contaminants was 14.40 hours and 23.18 hours, respectively (p-value <0.001).

Conclusion
An incubation period of 36 hours was sufficient to detect 100% of blood cultures positive for a pathogenic organism. Further research is needed to determine the impact of a shorter period of observation on hospital stay and antibiotic use.
Purpose

New advances in blood culture incubation systems – continuous monitoring blood culture systems (CMBCS) – now allow for more precise determination of blood cultures’ “time to positivity” (TTP). We aimed to determine whether a period of 36 hours (instead of the traditional 48 hours) was sufficient to detect all blood cultures positive for pathogenic bacteria in infants between the ages of 0 and 90 days presenting to the emergency department (ED) of an urban tertiary care pediatric center and undergoing a septic workup.

Methods

We performed a retrospective study of all positive blood cultures collected in the ED from infants 0 to 90 days old, over a 5-year time period (from March 13th 2008 to July 29th 2013). In our institution, blood culture bottles are received and incubated 24 hours a day, 7 days a week in a CMBCS (VersaTREK; Thermo Scientific). The TTP was calculated using the time interval from blood culture registration into the system to the time of gram stain, obtained from the microbiology Laboratory Information System (SoftMic, Medisolution). Medical charts were reviewed using a standardised data collection form to obtain relevant clinical information. With the help of a microbiologist-infectious disease specialist and a pediatrician, cultures were further divided into pathogenic or contaminant, based on organism and clinical presentation.

Results

Three thousand five hundred fifty-nine (3,559) blood cultures were collected from infants 0 to 90 days old in the ED during the study period. Of these, 98 (2.8%) were positive, collected from 96 infants (64 boys; 34 girls) with a mean age of 40.4 days. Among these positive cultures, 52 (53.1%) were deemed pathogenic and 46 (46.9%) were deemed contaminant, for a true prevalence of bacteremia of 1.5%. At 24, 36, 48, and 50 hours of incubation, 87.8% (86/98), 96.9% (95/98), 99% (97/ 98), and 100% (98/98) of all cultures were positive, respectively. If we consider only those organisms deemed pathogenic, at 24 and 36 hours respectively, 96.1% (50/52) and 100% (52/52) were positive. Mean TTP for pathogens and contaminants was 14.40 hours and 23.18 hours, respectively (p-value <0.001).

Conclusion
An incubation period of 36 hours was sufficient to detect 100% of blood cultures positive for a pathogenic organism. Further research is needed to determine the impact of a shorter period of observation on hospital stay and antibiotic use.
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