This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
SABE is most commonly due to:March 2013 
Select and explain. 
A. Staphylococcus aureus, B. Streptococcus pneumonia, C. Streptococcus viridans, D. HACEK group bacteria
B: Streptococcus pneumonia
Answer: B: Streptococcus pneumonia 
Explanation: B i.e. Streptococcus viridansSubacute bacterial endocarditis/Endocarditis lentaIt can be considered a form of Type III hypersensitivity.It is usually caused by a form of streptococci viridians bacteria that normally live in the mouth and throat (Streptococcus mutans, mitis, sanguis or milleri).Osler's nodes can indicate this condition.Nail clubbing is also often seen in subacute endocarditis.In cases of subacute bacterial endocarditis, the causative organism (streptococcus viridans) needs a previous hea valve disease to colonize and cause such disease.On the other hand, in cases of acute bacterial endocarditis, the organism can colonize on the healthy hea valve, causing the disease.