interpretation of blood culture gram stain/prelim

[europeman]

Can someone point me to a source where I can learn how to clinically interpret blood culture preliminary data.

for example, if my blood culture grows back gram possive cocci in clusters in 8 hours... .what difference should i be thinking if its in the aerobic vs anearobic bottle? how about cocci in chains?

likewise for gram negatives?

i'm a surgeon.... so i'm actually even more interested generally for bugs which primarily are related to surgery. thanks

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[Hernandez]

link

Surgery short-cut.
Gram pos - Vanco
Gram neg - Zosyn
Unsure - Vanco + zosyn

 

[bonadoc]

Can someone point me to a source where I can learn how to clinically interpret blood culture preliminary data.

for example, if my blood culture grows back gram possive cocci in clusters in 8 hours... .what difference should i be thinking if its in the aerobic vs anearobic bottle? how about cocci in chains?

likewise for gram negatives?

i'm a surgeon.... so i'm actually even more interested generally for bugs which primarily are related to surgery. thanks

wow, well here goes:

gram positive cocci in clusters is staph and in the hospital equals MRSA
gram positive cocci in pairs or chains is strep typically
gram negatives depend on what you see whether rod, coccobacillus, diplococci (e.coli, haemophilus, or neisseria) but there are others as well. You will pick up on it quickly though.

 

[europeman]

hi. thanks for the reply. that link isn't working for some reason.

i am actually asking for a source to learn a lot more in depth from the basics. i'm well aware of the clusters = staph kinda thing. but, in surgery, i need to be more savy with regard to enteric and other hospital infections. i.e. pseudomonus vs acinetobacter vs klebsiella. Haemophilus is generally not something which is a problem.

that said, i need some method of clinically thinking about these bugs in the context of a post operative, septic patient with gram stains from blood/body-fluid.

gram positives in surgery, for example, are often enteroccos. are some bugs more "stainable"? do some come back quicker tha others? are there questions i can ask the lab to help me get more precise preliminary guesses? thanks!

 

[Hernandez]

hi. thanks for the reply. that link isn't working for some reason.

The whole website seems to be down at the moment. try again in a day or two. The link is basically a pocket book of gram stain and types broken down into a nice little chart.

that said, i need some method of clinically thinking about these bugs in the context of a post operative, septic patient with gram stains from blood/body-fluid.

Probably the best you'll really be able to do is location of the infection and source fluid that you're culturing and just start very broad coverage with ABX and scale back as needed.

gram positives in surgery, for example, are often enteroccos. are some bugs more "stainable"? do some come back quicker tha others? are there questions i can ask the lab to help me get more precise preliminary guesses? thanks!

I doubt you'll really find anything along this line of thinking that will really be all that useful unless your REALLY know your microbiology. Even as an internist who deals with a ton of mirco in the MICU, or even on our surgical pts that magically get changed over to the medicine service after 3 days post-op, I've not found any great ID type of reference which will get me any quick prediction as to what type of bug it will be based off anything other than location of infection and gram stain and shape.

 

[dragonfly99]

I think Hernandez is right...
also, the prelim results are preliminary for a reason...sometimes they end up changing. Usually there is only a one day difference between prelim results and final results as well.
If you are not sure and the patient is very sick, and is hospitalized, esp. in the ICU, often you just have to start out with broad coverage and then narrow it down when you know more specifically what the patient has.

For less sick patients, I use a different strategy. For example, some residents will just give vancomycin to every patient who shows a hint of cellulitis anywhere, but a lot of them will get better with a less "big gun" antibiotic.
For MICU patients with gram + cocci in clusters, you just kind of have to assume it could be MRSA until proven otherwise...if it later comes back the next day as coag neg. staph and seems to have been a contaminant (based on patient's clinical status, etc.) you can always take off the vancomycin...

 

[bigtuna]

gram positive cocci in pairs or chains is strep typically

dont forget to think of enterococcus (VRE) here