Most Common Cause of Secondary Pneumonia

[Frozengrapes]

In Pathoma, Dr. Sattar refers to Strep pneumoniae as the most common cause of secondary pneumonia and Staph aureus as the second most common cause. I've read conflicting information across the board, with UWorld, Pathoma, and Phloston's lecture notes.

At this point, I'm inclined to go with Phloston, but does anyone know which is mostly accepted as correct on NBME/USMLE?

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[dyspareunia]

UWorld says strep pneumo, doesn't it?

 

[Medschool2323]

For what age group?

 

[Handinhand]

If by secondary you mean post-influenza infection, then the most common causes in order are staph. aureus, h. influenza, strep. pneumo.

 

[Frozengrapes]

If by secondary you mean post-influenza infection, then the most common causes in order are staph. aureus, h. influenza, strep. pneumo.

Thanks, and yes- sorry for not clarifying- by secondary I meant post-viral.

They don't usually specify an age group for the secondary pneumonia, I don't think.

 

[Frozengrapes]

UWorld says strep pneumo, doesn't it?

Yes, I believe it does. I've just read Staph aureus as being the MCC as well.

 

[Enzymes]

Yeah, I can never find a good answer to this. I would go with Strep Pneumo as #1 myself. But I think what is more important is that there will be other clues in the vignette that will help you distinguish between organisms. I doubt that USMLE would ask a question without giving some clues about which organisms they are dealing with. Like abscess in the lungs is more likely staph aureus.

 

[thehundredthone]

According to this article, although a few of the studies done during various influenza outbreaks found S. aureus to be more common, most studies found S. pneumoniae to be more common.

Also,

Evidence from in vitro studies has demonstrated the lethal synergism between influenza virus and S. pneumoniae. Influenza virus infection has been shown to prime for the development of lethal pneumococcal pneumonia and bacteremia in a dose-dependent fashion in a mouse model.

 

[AnastomoSteve]

UW QID 1666

S. pneumo, S. aureus, H. influenzae

Although I remember learning it as S. aureus during the school year...

 

[Handinhand]

First aid lists it in the order that I have posted above, which is what I'll be using on Step 1. Having gone through UWorld twice now, it's definitely not without its errors...

In reality, I highly doubt you're going to get a question without SOME kind of defining criteria of the bug (gram pos cocci in clusters for example)

 

[dyspareunia]

If by secondary you mean post-influenza infection, then the most common causes in order are staph. aureus, h. influenza, strep. pneumo.

First aid lists it in the order that I have posted above, which is what I'll be using on Step 1. Having gone through UWorld twice now, it's definitely not without its errors...

In reality, I highly doubt you're going to get a question without SOME kind of defining criteria of the bug (gram pos cocci in clusters for example)

What page? Because if you're talking about FA14 page 171 it just lists them. It doesn't say they are in any particular order. It seems logical to assume they listed them in order of most common to least common, but I don't think you should make that assumption. Look at the list for nosocomial (on page 171); they list staph, pseudomonas, GNB. Yet, on page 629 the list for nosocomial pneumonia is kleb, ecoli, pseudomonas. Clearly they aren't listing things in any particular order.