Infective Endocarditis (SBE, ABE) Flashcards Preview

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IE diagnosis

Positive blood cultures are the cornerstone of the diagnosis.

Three sets of blood cultures detect 96-98% of bactremia. Since the bactremia of IE is continuous, there is no reason to time the culture with fever or chills. Three sets of cultures from different sites should be obtained PRIOR to the initiation of antibiotics.


IE cultures

The diagnostic yield of more then 3 blood cultures is small, and can be confusing (contaminants, etc.)
Most clinically significant cultures are positive in 48 hours, an exception is slow growing bacteria like the HACEK group


IE Risk Factors

Age>60 years->50% cases
Male sex-3:2 to 9:1
Injection drug use
Poor dentition
Comorbid Conditions


IE Comorbid Conditions

1. Structural heart disease, Rheumatic
2. Valvular heart disease
3. Congenital heart disease
4. Prosthetic heart valves
5. History of IE
6. Presence of intravascular device
7. Chronic HD
8. HIV


IE, Clinical Manifestations

May present acutely, as rapidly progressive or more slowly as a sub acute or chronic disease.
Acute presentation may be due to the organism of infection (Staph aureus), it’s virulence, method of transmission (IV drug abuse) or host suspectibility (immunocomprised)


IE Symptoms and Signs

General symptoms of infection, malaise, chills, anorexia, joint pain, headache, etc
Cardiac murmur 85%, regurgitant if primary (that is due to the infection), but my develop on stenotic valves



Staphylococcus aureus-31%
Strep viridans-17%
Coag negative staph-11%
Strep bovis-7%
Other strep-5%
Non HACEK gram negative-2%

HACEK-2%, includes Haemophilus aphrophilus, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kingella kingae.



Haemophilus aphrophilus
Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kingella kingae.


IE Epidemiology

Increase in incidence from 2000 to 2011 from 11 to 15 cases/100,000 population


IE presents

Usually presents acutely not sub acutely (as before antibiotic age)
Careful clinical history focused on indwelling prosthetic devices such as; IV catheters, orthopedic hardware, cardiac devices.
IV drug use/abuse is one of the most important factors



PE should focus on new regurgitant murmurs and CHF
Look for stigmata of endocarditis to include, subungual hemorrhage, Roth spots, Janeway lesions, Osler nodes. Remember most of these are signs of sub acute, not acute disease and they will be absent.


IE diagnosis

Modified Duke criteria are used.
The diagnosis is usually straight forward if the pathogen is obtained on blood culture, it is likely to cause endocarditis and there is evidence of endocardial involvement.


IE Duke Criteria

Definite IE
Pathologic criteria
micro organism recovered from tissue (embolus, abscess, culture)
Histologic proof of organism
Clinical criteria
2 major or
1 major and 3 minor
5 minor


Possible IE Duke criteria

1 major and 1 minor
or 3 minor


Reject the IE diagnosis if...

firm alternative diagnosis or
resolution of manifestations with 4 days of antibiotics or

No pathologic evidence of IE at surgery or autopsy after only 4 days of Rx
Does not meet Duke criteria


Duke Major Criteria- blood cultures

Positive blood culture
Typical micro organism for IE from two separate blood cultures;
Viridans Strep
Strep gallolyticus (bovis)
HACEK group
Staph aureus
Community acquired enterocci or

Persistently positive blood cultures;
blood cultures drawn more then 12 hours apart, or
¾ positive cultures
Single positive culture for Coxiella burnetii or antiphase I IgG antibody titer >1:800

Evidence of endocardial involvement
Very important


Other duke major

Positive echocardiogram
New valvular regurgitation


Duke minor

Fever (100.4 F, 38 C)
Vascular findings
Immunologic findings
Positive blood cultures not meeting above major criteria
Serologic evidence of infection


Blood cultures

Obtain blood cultures prior to iniation of antibiotics, if feasible (“do no harm”)
At least 3 sets of cultures
Separate sites, not catheter
Typical organisms are Staph Aureus, viridian strep, strep bovis, enterococci and HACEK group.



Should be obtained in all patients, a TTE first, TEE if indicated