Viridans or Epidermidis in Prosthetic Heart Valves? - USMLE Forums
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  #1  
Old 04-13-2012
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Bacteria Viridans or Epidermidis in Prosthetic Heart Valves?

hey everyone,
What causes infective endocarditis due to prosthetic valves- is it S.viridans or S.epidermidis ? I am confused--FA mentions s.epidermidis, but in DIT lectures, he says subacute endocarditis can be caused by s.viridans on abnormal valves like prosthetic valve.
So which bacteria do we pick on usmle.
Please clarify..anyone.
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Old 04-13-2012
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Prosthetic valve IE of early onset is due to intra-op contamination- is caused most commonly by staph epidermidis (40% cases)

I think subacute prosthetic valve IE is more likely the late onset type and so there strep viridans is common.

Therefore I guess both references are correct.

Last edited by slumdog; 04-13-2012 at 07:26 AM. Reason: addition
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Old 04-13-2012
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In prosthetic valves - s. epidermidis
In previously damaged valves - s. viridans

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Old 04-13-2012
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yup prosthetic: s. epidermidis and previously damaged is s. viridans
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Quote:
Originally Posted by MedicalExaminer View Post
...
In previously damaged valves - s. viridans
....
I guess "abonormal valves such as prosthetic valves" and "previously damaged valves" do not convey same meaning.
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This is really confusing.
Staph Epidermidis -40-50% cause of IE in prosthetic valves.
Second most is Sterotococcus Viridan-5-20 %
but risk factors for Strept Viridans are: VSD with shunts, MS, AS, prosthetic valves, MVP, bicuspid aortic valve and marfan's syd.

I would go with Staph Epidermidis.
Please reply if you get authentic answer.
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Meh, cmon!

both can!!
it just depends on the history.

A gal with MVP brushes teeth and ends up in the ER anytime soon - Strep. Viridans.

A pal with prosthetic valve (especially metallic.... though for USMLE all the valves are metallic) who has a catheter - thats a candidate for strep epidermidis.

Damaged valve is a nice substrate for strep viridans. Metallic surface of the valve - strep epidermidis.

In the USMLE question you will either see a nice distinctive history or just one of these bugs in the answer choices if the history is unclear.
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^^yeh, that's what I was thinking. whenever a question mentions something related to teeth/mouth--->viridans. if not: epidermidis...
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Thanks everyone ....I hope they are either clear or not give both options in the choices.


I did some research..wikipedia does`nt mention anything about staph epidermidis. But damaged or abnormal valves include congenital problems, rheumatic heart disease, dental procedure sequelae etc which are prone to strep viridans but...staph epidermidis infects prosthetic valves. It must`ve been a slip up when the dr from DIT ( not dr.jenkins) mentioned strep viridans on prosthetic valves.
thanks for everybody`s input.
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