NBME 20 Streptococcus pneumoniae (NBME Answers)

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nbme20/Block 2/Question#14 (reveal difficulty score)
A 23-year-old woman has had fever, ...
Streptococcus pneumoniae 🔍 / 📺 / 🌳 / 📖
tags: micro

+7 upvote downvote
submitted by ∗chandlerbas(118)

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"However, in the years, the bacterial pattern of splenectomy sepsis have been changing. The most important capsulated pathogen is Streptococcus pneumoniae (Str. Pneumoniae), but Haemophilus influenza (H.Influenzae) and Neisseria meningitidis (N. meningitidis) are also significant. In a study of 1991,36 reporting 349 episodes of sepsis in patients with asplenia, 57% of infections and 59% of deaths were caused by Str. pneumoniae." https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4621170/

honestly i tried to find data to support E.Coli or any higher risk of gram - sepsis, but pneumo is still numero uno

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fatboyslim FA 2020 page 186: Asplenic patients (S. pneumoniae>> H. influenza > N. meningitidis) +2

utap2001 Maybe Gram(-) bacteria are more easy to induce sepsis. But concerning of frequency, Strep. pneumonia is most common in asplenia patient(respiratory transmission). +

+5 upvote downvote
submitted by ∗yotsubato(1208)

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This question is bullshit. The woman would most likely be vaccinated to Strep pneumo, especially if she had a splenectomy.

E coli is also an encapsulated bacterium that causes pneumonia, so that is more likely IMO.

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sugaplum I agree with you, only possible logic for their answer: the qualifier asplenic makes the "ShIN" pathogens more likely, even though Ecoli can cause gram negative sepsis and DIC. FA 2019 pg 127 Also it says s pneumo causes sepsis specifically in asplenic patients Pg 136 +1

lmfaoayeitslit To be honest, the only reason I got this right (because I really was thinking E.Coli as well), is that I ended up remembering the MOPS part of the Sketchy, and I couldn't remember if he said that it was the number 1 cause of all of them or not, and ended up clicking it. It's pretty shitty they don't offer explanations for these. +

merpaperple I thought this too but it seems like Strep pneumo is just more specifically associated with infection in asplenic/sickle cell patients than E. Coli is. Just one of those classic associations. There's a sickle in the Sketchy Strep pneumo sketch, vs. no sickle in the E.Coli sketch. +1

drzed E. coli causes pneumonia by aspiration, for which this patient had no risk factors. For USMLE, if they don't say the patient is vaccinated, you can assume they are NOT. Just because she has a history of splenectomy following trauma does NOT mean she had to been vaccinated--don't fill in the history for the patient, only use the information they give you. +1

vivijujubebe also DIC more often seen with G- bacteria right???? That's why I chose E.coli instead of S.pneumonia +3

+2 upvote downvote
submitted by ∗monoloco(155)

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Encapsulated organisms run rampant in patients who have no spleen, whether physically or functionally. (Recall the wide-array of sequalae sickle cell patients experience thanks to their functional autosplenectomy.)

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sympathetikey Agreed -- went with E. Coli like a dingus, just because I didn't associate DIC with S. Pneumo. Thought it was too easy. +

chillqd Isn't E. Coli also an encapsulated organism? What makes Strep pneumo more likely in this question just because its the more common cause? +28

studentdo Pseudomonas aeruginosa is encapsulated as well. I think the right answer has to do with DIC but why? +1

mgoyo89 The only reason i found was S. pneumo is more common, I went with Pseudomonas because of the "overwhelming sepsis" :( +2

kard Everyone is correct about the Encapsulated microbes, but this is one of those of "MOST LIKELY", and by far the most likely is S.Pneumo>>H.infl>N.Mening. (omitting that patients with history of splenectomy must be vaccinated. +2

djinn Gram negative are more common in DIC my friends +2

drzed Correct me if I am wrong, but I am pretty sure that E. coli is NOT a common cause of pneumonia because it must be aspirated to enter the lung. Thus, only patients with aspiration risk (e.g. stroke, neurogenic conditions) would be at a chance of getting E. coli pneumonia. +2

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