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NBME 20 Answers

nbme20/Block 2/Question#8

Three elderly residents of an assisted living ...

Legionella pneumophila

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Legionella is common causes of pneumonia superimposed on chronic obstructive pulmonary disease.

asapdoc  Im pretty sure so is strept pneumoniae +2  
usmleuser007  COPD is also exacerbated by Viral infection: Rhinovirus, influenza, parainfluenza; and Bacterial infection: Haemophilus influenzae, Moraxella catarrhalis, Streptococcus. however, the questions gives a hint that it may be legionella = "weekend retreat" which may be associated with this infection +1  
loopers  From FA 2017 pg 139: Legionnaires’ disease—severe pneumonia (often unilateral and lobar A ), fever, GI and CNS symptoms. Common in smokers and in **chronic lung disease.** +1  
kentuckyfan  I also believe that the other attendees showed signs of pontiac fever, which is another hint they tried to get at. +1  
luke.10  i did it wrong and chose influenza virus since it is most common infection in COPD but the clue in the Question is that the other attendee didnt get sick since in legionella there is no person to person transmission +  
endochondral   but in Uworld s. pneumo is one of the most common bacterial exacerbation of COPD legionella wasn't even mentioned. How do we rule out s. pneumo ? +1  
nala_ula  maybe because in children s.pneumo causes otitis media? +  
smc213  Another hint made in the Q stem is the location being rural Pennsylvania.... Legionnaires disease was first discovered by the outbreak in 1976 at a convention held in Philadelphia, Pennsylvania. Not sure why I know this fact... +1  
hpsbwz  Biggest hint towards legionella to me was that they all were at a residence hall... i.e. where there'd be air conditioners and such. +2  


Legionella pneumophila and Mycoplasma pneumoniae causes WALKING pneumonia aka you have pneumonia and you dont care (none of them require hospital care. that was my key point

+/- usmlecrasher(1),


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submitted by usmle11a(11),

legionella : very common in advanced age, COPD, immunosuppressed patients and " going back from a residence hall" which probably had a contaminated AX system (basically fits every one in the Q)

adeno X : would present with conjunctivitis, throat pain ... flu virus: not everyone got the disease RSV: no children strep pneumo: would target a larger population of healthy people as well.