Microbiology-Infectious Endocarditis Flashcards
What are the two types of endocarditis and what determines what type you have?
Acute and sub-acute endocarditis. The infections are classified based on the virulence of the infecting organism. Acute and sub-acute can both result in heart failure and renal disease.
What are potential sources of bacterial that can cause infective endocarditis?
Breach of barrier from normal flora, infection elsewhere in the body and IV drug use.
What makes a host susceptible to infective endocarditis?
Preexisting valvular damage (due to sticky fibrin deposition on valve). Prosthetic valve replacements. Infection by an aggressive microbe.
Incidence of endocarditis involving native valves is only 5 per 100,000. What age group is most likely to become a case?
Aged 50-70
What is incidence of endocarditis in I.V. drug users?
150 to 2000 cases per patient-year
Why is poor dentition and oral hygiene a risk factor for infective endocarditis?
The bacteria in your mouth exist in biofilms that stick very well to fibrin on valves.
What is the #1 predisposing factor for endocarditis in the developing world?
Rheumatic fever
Who is the offender in endocarditis that presents after an impetigo infection?
Group A strep (pyogenes). Note it is gram-positive, beta-hemolytic, catalase negative and bacitracin sensitive.
What is responsible for deposition and thickening of valve leaflets in rheumatic heart disease?
Antibodies developed against the M protein attack valve leaflets.
What are the different types of bacteremia?
Transient (bacteria readily cleared w/o detectable inflammatory response), intermittent (infection from extra-vascular site spreads and causes inflammatory response), continuous (infection site within circulatory system)
A patient comes to see you with a fever and general malaise. She also presents with splinter hemorrhages in her nail beds and eyelids. What does this tell you?
She likely has an infective endocarditis because antigen-antibody complexes are blocking the capillaries and causing these splinter hemorrhages.
A patient presents with fever and general malaise. His palms and soles of his feet are shown below. What are these lesions and what do they tell you?
These are Osler’s nodes (left) and Janeway’s lesions (right). They indicate embolism of fibrin, antigen-antibody complex and/or bacteria to these distal sites. Osler’s nodes will be very tender and Janeway’s lesions are non-tender.
Where is the most common site bacteria infects the heart?
Left side (aortic and mitral valves). Congenital and acquired lesions predominate on the left side of the heart, endothelia are more prone to damage on this side and oxygen content is high and can promote growth.
What side of the heart is most often affected by IV drug use?
Right side. This accounts for 10% of infective endocarditis.
What are common complications seen from infective endocarditis?
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What are the usual bacterial culprits in people with native valves? Prosthetic valves? IV drug abuse?
Early prosthetic valves are subject to nosocomial skin pathogens, later on they carry the same risk ask native valves.
A patient who is recovering from a heart valve replacement shows signs of endocarditis. He has been on a central IV line for the past few days. Lab results show a gram-positive, catalase positive, coagulase negative non hemolytic bacteria. What is the offending organism in this case? What if were staph aureus?
Staph epidermidis. It is common in hospital settings because it can form biofilms on sites where catheters stay for a while.
What type of organisms are suspected when endocarditis is associated with GI cancers and urogenital infections?
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How do you diagnose infective endocarditis?
DUKE criteria. 2 positive bacterial blood cultures and echocardiogram.
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How do you differentiate staph, strep and enterococcus?
