Thread by @andreaprinzi

1/ Proud to be a part of this hot-off-the-press #stewardship study examining time to blood culture positivity by pathogen and primary service. A joint effort by scientists at @ChildrensColo @CUMedicalSchool @CUAnschutz. Check it out #IDTwitter ! Summary 🧵
pubmed.ncbi.nlm.nih.gov/34407980/#:~:t…

2/ Some background:
* Historically, infants and children are given antibiotics until blood cultures are negative at 48-72 hours.
*Empirically treating is essential for children with bacteremia, but waiting for this negative BC period may be unnecessary. pubmed.ncbi.nlm.nih.gov/25567785/

3/ Why we did this study:
* Understanding the time it takes for blood cultures to become positive (with respect to certain organisms and subspecialties) can help shorten overall antimicrobial duration.

*Shortening duration= fewer adverse events, less resistance, shorter stays

4 / What we did:
* Retrospective analysis of 6,184 blood cultures with positive results over a 6-year period at a large quaternary-care pediatric hospital.
* Included:
-All pts who had BC drawn from Jan 2013- Dec 2018
-Only 1st pos results included

5/ What we did (continued)
*A cx was considered a 1st pos if it had a new organism or if 2 weeks had elapsed since previous positive cx.
*Demographic and #microbiology data were collected
*Cx collect date and date/time that growth was first reported to providers collected

6/ The #microbiology
*#Lab uses standardized BC methods
*Routine BCs incubated for 5 days
*When pos --> Gram stain, BCID (PCR), sub-cultured to BAP/MAC/CHOC/BRUC & incubated (and specialty media added as necessary i.e., chromogenic media or CNA)

7/ The #microbiology continued...
* Media plates incubated for 18-24 hours and examined for growth.
*Orgs identified by MALDI-TOF MS and/or basic biochemical methods

8/ How we categorized things:
*Organisms were categorized into Gram-positive definite pathogens, Gram-negative definite pathogens, Gram-positive possible pathogens, yeast, common contaminants, and "other uncommon definite pathogens" (<30 BCs + for that org during study period)

9/ How we categorized things, continued:
* Possible pathogens were defined as those treated by the primary team with directed antimicrobial agents >= 3 days
* Contaminants defined as those that were either not treated, or treated <3 days

10 / The stats:
*Time to positivity (TTP) was calculated based on the date/time a cx was collected and when the GS was first reported by microbiology to the clinician.
*# of pts who would need to be treated for 48 hrs vs 36 to prevent 1 case of abx termination before pos result

11/ Results
*After exclusions, 2,148 positive BC results were analyzed
* 69% grew definite or possible pathogens
*31% grew common contaminants
*68% of cultures were pos at 24 hours
*87% of cultures were pos at 36 hours
*93% of cultures were post at 48 hours

12 /
* When looking at ALL blood cultures obtained during the 6-year period (89,663), only 125 cultures (0.14%) were positive between 36 and 48 hours.
* The median TTP for all included BCs positive for bacteria during this study period was 19.83 (14.4-26.0)

13 / Broken down by organism category, median TTP:
* Gram-pos definite = 15.93 (13.06-19.41)
*Gram-neg definite = 14.33 (11.60-18.35)
*Gram-pos possible = 20.74 (14.36-25.80)
*contams = 24.48 (21.19-32.27)
*yeast = 32.50 (20.08-44.54)
*uncommon paths = 24.90 (17.67-39.07)

14/ Sub-specialty analysis was also performed based on the patient's treatment team:
Of the 2,121 pts with 1st pos blood cultures:
*21% = Hem/Onc/BMT
*15% = PICU
*10%=GI
*14% = NICU
*9% = CICU
Remainder = hospital medicine service

15 /
*When comparing the TTPs for all treated pathogens among the NICU, PICU and CICU, there wasn't a difference between groups

*Longer median TTPs were observed in the NICU with MSSA, MRSA, and Streptococcus species.

16 / Putting it all together:
1. This study suggests that 36 hours is sufficient for observation of blood cultures in infants and children who are receiving empiric antimicrobial treatment out of concern for bacteremia (87% of BCs positive by 36 hours).

17/

2. This study suggests that early de-escalation is appropriate in a clinically stable patient. This will likely require safety-netting with robust education, strict return precautions, etc.

18/

3. The longest median TTP in this study was for yeast, at 32.50 hours.

4. There was no significant difference in TTP w/ respect to source (CVC vs peripheral draw) or treatment team.

**These findings are consistent with previously published literature

19 / Why is this unique?
Size, pathogen type 🦠, treatment team💊!
To quote from the manuscript:
With this study, we wanted
to address the common statement heard on
#stewardship rounds of “that study was not
done in patients similar to mine.”

20/
If you just want the overarching conclusion of the study, it's this:
"The probability of true bacteremia after 36 hrs is low enough that the # of children needed to be treated beyond that time window to prevent 1 case of
premature termination is likely excessive"
#Stewardship

21/ The impact:
If practice was changed to 36 hours hospital-wide, thousands of days of unnecessary antimicrobial therapy could be avoided, also reducing associated downstream effects of such therapy.
#IDTwitter

22/
This was led by PharmD extraordinaire @ChristineMacBr1 and senior authored by the one and only @HandshakeASP -- both of which run a powerful #stewardship team at @ChildrensColo. Work would not have been possible without Manon Williams, Kelly Pearce and Dustin Lamb as well.

And for those who would like it all wrapped up nice and pretty...

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