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Old 06-28-2011
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Question what's the identity of causative agent?

An active intravenous drug abuser presents to the emergency department with fever of 5 days' duration, a cough occasionally productive of blood, and pleuritic chest pain. Petechiae are present in his mouth and conjunctivae, and splinter hemorrhages are visible under the fingernails. Which of the following test results would most likely confirm the identity of the causative agent?

A. Antibodies to p24 capsid antigen
B. Antibodies to Trichinella spiralis antigen
C. Blood culture of a catalase-positive, novobiocin-sensitive, gram-positive coccus
D. Blood culture of a coagulase-positive, catalase positive, gram-positive coccus
E. Blood culture of a gamma-hemolytic, gram-positive coccus on bile-esculin agar
F. Blood culture of an alpha-hemolytic, optochin-resistant, gram-positive coccus
G. Blood culture of an alpha-hemolytic, optochin-sensitive, gram-positive coccus
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Old 06-28-2011
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D. Staph. aureus, most common cause of IE in IV drug abuser
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Old 06-28-2011
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I ll go for D indicating staph aureus.
just for info..,
A: HIV,
B: Trichinella,
C: Staph epider
D. S.aureus
E enterococci
F: Strep. mutans
G: Strep. pneumo
correct me if i am wrong..!!


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Originally Posted by earthpole View Post
An active intravenous drug abuser presents to the emergency department with fever of 5 days' duration, a cough occasionally productive of blood, and pleuritic chest pain. Petechiae are present in his mouth and conjunctivae, and splinter hemorrhages are visible under the fingernails. Which of the following test results would most likely confirm the identity of the causative agent?

A. Antibodies to p24 capsid antigen
B. Antibodies to Trichinella spiralis antigen
C. Blood culture of a catalase-positive, novobiocin-sensitive, gram-positive coccus
D. Blood culture of a coagulase-positive, catalase positive, gram-positive coccus
E. Blood culture of a gamma-hemolytic, gram-positive coccus on bile-esculin agar
F. Blood culture of an alpha-hemolytic, optochin-resistant, gram-positive coccus
G. Blood culture of an alpha-hemolytic, optochin-sensitive, gram-positive coccus
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  #4  
Old 06-28-2011
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answer is D
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  #5  
Old 06-28-2011
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The patient is exhibiting the classic signs of acute bacterial endocarditis. In intravenous drug abusers, Staphylococcus aureus is the most common causative agent, because it is the most common normal flora organism on the skin of these patients, and choice D is the classic description of this species. Catalase positivity distinguishes the genus Staphylococcus from Streptococcus, and Staphylococcus aureus is the only coagulase positive member of its genus. Antibodies to p24 capsid antigen (choice A) would be likely in an HIV-positive drug abuser, rather than a patient with endocarditis. Trichinella spiralis (choice B) can cause splinter hemorrhages during the larval migration period, but would not be the most likely agent given the other symptoms. Staphylococcus epidermidis is a catalase-positive, novobiocin-sensitive, gram-positive coccus (choice C). It is sometimes implicated in subacute bacterial endocarditis, but is less common as a causative agent in drug abusers than in normal individuals. Enterococci are gamma-hemolytic, gram-positive cocci that grow on bile-esculin agar (choice E). Enterococci can cause subacute bacterial endocarditis, chiefly after urologic instrumentation in men, rather than in association with intravenous drug abuse. Streptococcus viridans is an alpha-hemolytic, optochin-resistant, gram-positive coccus (choice F). It is implicated in subacute bacterial endocarditis after oral or dental treatments but would not be the most likely agent, given the acute nature of this patient's presentation.
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