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@rabihmgeha shared a fantastic approach to positive BCx! I use a similar schema, but add ‘Questions to ask the lab/what to do next?’ since #ID usually doesn’t get the ‘critical result’ call from micro, and I want to empower those who do with actionable knowledge.
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2/ I arrange the potential Gram stain results that one can be called w/ as follows: Gram(+) cocci, Gram(+) rods, Gram(–) rods, Gram(–) cocci, yeast. Gram(+) cocci are grouped by ‘morphology’ since the lab usually tells you this: clusters, pairs, chains, etc. Fill in with orgs.pic.twitter.com/kZl5LDliXW
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3/ Like
@rabihmgeha's schema, the orgs are deliberately ordered this way: Gram(+) orgs are often [skin] contaminants, Gram(–) orgs & yeast are not. Remember that clinician adjudication is the ‘gold standard’ for deciding what is a contaminant!pic.twitter.com/38BhCKlHXu
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4/ Now, w/ the bugs organized, when you get that call from the micro lab, here are 3 questions to ask yourself/the lab: 1) Number of positive bottles/cultures and time to positivity? 2) ‘Shape’ of the bacteria? 3) Aerobic or anaerobic bottle? Let’s break these questions down.
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5/ Fewer positive cultures & longer time to positivity suggests a contaminant. Apply Q1) to Gram(+) orgs. Time to positivity tough to interpret unless extreme (ex. 8h v 48h). Can use # of positive cx fact to your advantage – before abx, obtain more cx & increase the denominator!pic.twitter.com/yKBm6c3I9H
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6/ Apply Q2) to Gram(+) rods since their shapes are so distinct. There are some uniquely shaped Gram(–) rods too, but rare (think Fusobacterium). Here’s a comparative chart of GPRs to illustrate. A great reason to go to micro lab and review the Gram stain!pic.twitter.com/jK29be5884
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7/ Apply Q3) to Gram(+) rods & perhaps Gram(–) rods too. For GPRs, preferential growth in the aerobic v anaerobic bottle helps organize the ‘shape’ chart. Ex: while you await speciation for that aerobic box car shaped GPR, these clues suggest Bacillus, usually a contaminant!pic.twitter.com/MtawF0EUnA
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8/ For Gram(–) rods, the pearl is that Pseudomonas is a ‘strict’ aerobe and ought to grow preferentially in the aerobic bottle – thus, a GNR that grows in the anaerobic bottle first is less likely Pseudomonas. Of course, always exceptions to these pearls, so await speciation!
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9/9 Let’s put all this together in a final summary chart. I have to give credit to
@colleenkraftMD for teaching me this approach as a fellow! What do you think#IDTwitter?@CarlosdelRio7@Ahmed_HBabiker@serotavirus@natesumMRSA@CPSolverspic.twitter.com/XH4xGruLT4
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Wonderful chart Dr. Phadke- hope you don't mind we made this image shareable for others to find and bookmark outside of twitter "blood culture interpretation" ->https://www.grepmed.com/images/6137
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