In the case presented, the 60-year-old woman has a history of rheumatoid arthritis and a prosthetic aortic valve, and her symptoms include lethargy, confusion, fever, chills, headache, and neck pain. Given her history of a prosthetic valve, she is at increased risk for infective endocarditis.
The most likely causative organism associated with infective endocarditis in individuals with prosthetic valves is Staphylococcus epidermidis, which is a