Strep viridans bacteremia

It happens, from time to time, that a patient who is febrile, hypotensive, confused, or otherwise acutely ill has blood cultures drawn and is found to have Strep species in them.  A short time after that, the lab may call the ward and give further identification - the Strep belong to the viridans group.

The reflex reaction to this may be - does this patient have endocarditis??  It's an important question to answer.  Traditional teaching about Strep viridans is that it is the primary causative organism of what we used to call "subacute" bacterial endocarditis.  While we don't look at endocarditis quite the same way any more, it is still true that viridans bacteremia is a major diagnostic criterion under the Duke system of estimating the likelihood of infective endocarditis.

However, that's not the end of the story with Strep viridans.  It has important other sources, primarily in the gut and oral cavity.  When it arises de novo, one should ask the following questions:

1.  Could this patient have infective endocarditis?  (note - IE hasn't given up first place!)
2.  Is there a possibility of an underlying cancer involving the mouth or GI tract?
3.  Is this a patient with impaired immunity?  (these bacteremias may occur more easily, for example, in patients with hematologic malignancies, with or without chemotherapy)
4.  Does the patient have an indwelling vascular access device?
5.  Irrespective of 2 through 4, could this patient have infective endocarditis?

A recent paper (from Slovakia)  [Mrazova, et al. "Prospective national survey of viridans streptococcal bacteraemia risk factors, antibacterial susceptibility and outcome of 120 episodes" Scandinavian journal of infectious diseases (2005)] shows a current snapshot of the associations of different diseases with Strep viridans bacteremia.

The rule of thumb regarding treatment of Strep viridans bacteremia should be followed here:  When in doubt, and when there is no compelling contraindication, treat this as infective endocarditis, according to current guidelines.