Which organism is typically associated with endocarditis following dental cleaning in a patient with a native valve?

Streptococcus viridans is the organism typically associated with endocarditis that follows dental procedures, particularly in patients with native heart valves. This group of bacteria is part of the normal flora found in the oropharynx and comprises species such as Streptococcus mutans and Streptococcus sanguis.

During dental cleaning, transient bacteremia can occur, whereby these bacteria enter the bloodstream. In individuals who have predisposing factors such as congenital heart defects or damaged heart valves, these bacteria can adhere to the valvular endothelium and lead to the formation of vegetations, which is characteristic of infective endocarditis.

The mechanism by which Streptococcus viridans causes endocarditis is primarily related to its ability to form biofilms on heart tissue and its relatively low virulence, which allows it to persist in the bloodstream and propagate infection, especially when there is existing cardiac abnormality. The other organisms listed, while they can cause endocarditis, are more commonly associated with different clinical scenarios. For example, Staphylococcus aureus is often linked to endocarditis in intravenous drug users or those with prosthetic valves rather than native valves following dental procedures.