USMLE-Rx Step 1 Practice Q's

USMLE-Rx Step 1 Qmax Challenge #4130

Check out today’s Step 1 Qmax Question Challenge.

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USMLE-Rx Step 1 Qmax Challenge #4130A 75-year-old man presents with a few weeks of fever and chills. He has hypertension and takes medicines daily to lower his blood pressure and cholesterol, although he cannot remember their names. He is otherwise healthy, although his wife comments that he underwent a dental procedure a few weeks ago. Patient admits that he was supposed to take antibiotics, but was unable to complete course of antibiotics. On physical exam, you find painful, red, raised lesions on his fingers, like that shown in the image.

Which of these is most likely causing this man’s condition?

A. Haemophilus influenzae
B. Staphylococcus aureus
C. Staphylococcus epidermidis
D. Streptococcus pyogenes
E. Viridans streptococci

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11 replies »

  1. The correct answer is E. Viridans streptococci are normal flora of the oral cavity and can cause subacute bacterial endocarditis, one of the symptoms of which is Osler nodes, as shown in the image. Prophylaxis against viridans streptococci should be initiated before dental procedures in patients with artificial heart valves and/or other risk factors for bacterial endocarditis.

    A is not correct. Haemophilus influenzae does not commonly cause endocarditis and is not part of normal oral flora, and thus prophylaxis for it is not needed before oral procedures in those with artificial heart valves.

    B is not correct. Although Staphylococcus aureus may cause endocarditis, prophylaxis against S. aureus is not usually needed before dental procedures in patients with artificial heart valves.

    C is not correct. Staphylococcus epidermidis can cause endocarditis on artificial heart valves. In such cases it generally gains access to the bloodstream through intravenous or arterial lines in hospital. It is not part of the normal oral flora, and thus prophylaxis for it is not given before oral procedures in those with artificial heart valves.

    D is not correct. Streptococcus pyogenes does not commonly cause endocarditis.

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