Flashcards in Micro- Infective Endocarditis Deck (78):
Infection of the heart chambers or valves (endocardium)
List the 4 Classes of Infective Endocarditis
Native Valve Endocarditis NVE
Prosthetic Valve Endocarditis PVE
Health Care Associated Endocarditis HCIE
Intravenous Drug-use Endocarditis IVDU
Two forms of NVE
Acute : Involves normal valves. Quick insidious onset.
Subacute: Involves previously damaged valves. Occurs more slowly than acute.
Two forms of PVE
Early : Within 60 days
Late: After 60 days
When can we can consider IE Nosocomial (HCIE) ?
If the infection occurs 72 hours or more past admission. (If it occurs during the first 72 hours it is likely that the patient had a pre-existing infection)
Mitral valve (only) involvement in IE ?
Tricuspid valve (only) involvement in IE ?
Aortic valve (only) involvemtn in IE ?
5-36 % (2nd most)
Aortic and Mitral Valve involvement in IE ?
0-35% Quite common
Pulmonary valve involvement in IE ?
Less than one percent
Are the valves damaged before the onset of IVDU endocarditis ? Is onset acute or subacute ?
No, they are healthy.
List causes for damage to valves that would predispose someone to a sub-acute NVE ?
Rheumatic Fever (6%)
Calcific Aortic Valve (50%)
Congenital heart disease (15%)
Ventral Septal Defects
Patent ductus arteriosus
Tetrology of Fallot
Describe the initial steps of infection once the valve surface is disrupted
Valve surface disruption --> Platelets and Fibrin adhere (Non-Bacterial Thrombotic Endocarditis) -->Bacteria adhere to NBTE --> Increased build up
Sources of Bacteria that cause IE include :
Mouth : Dental work, poor hygiene
Lungs: Pneumonial infections
GI: Gastric procedures (colonoscopy
GU: Catheters etc.
Most likely family of Bacteria to cause IE ?
Staphylococci (42% of all IE cases)
Mainly S.aureus (31% of staph cause IE. Most common pathogen overall in IE) but also CoNS species
Streptococci acount for nearly 40% of all IE's. What species are most prevalent
Viridans (17 %)
Enterococci (11 %)
Main pathogen for NVE ?
Viridans, Bovis, Enterococcus
List the three main organisms resonsible for ACUTE NVE ?
Staph Aureus (abscess with pus formation)
Strep. Pneumoniae (rapid, heavy immune response)
Strep. Pyogenes ((rapid, heavy immune response)
List the two main groups responsible for SUBACUTE NVE ?
Main pathogens associated with PVE
Coagulase Negative Staphylococcus (30%)
S. aureus (usually nosocomial as MRSA), mosly Early
Strep (Late PVE )
Which organisms are associated with LATE PVE ?
Which organisms are associated with early PVE ?
CoNS and S.aureus
Most common pathogen associated with IVDU endocarditis ?
Also, involved are :
A,C and G Streptococci
Common organisms associated with HCIE (hospital acquired)
Which organisms that cause IE produce Dextran ( a virulence factor that is part of bacterial capsule and helps in adhesion)
Which organisms that cause IE produce FIM-A , a virulence factor that mediates attachment to the forming thrombus fibrin/platelet matrices on valves ?
Molecules that allow for adhesion of bacteria to NBTE ? (found on/in thrombus)
Type 4 collagen
Platelet aggregation is stimulated by Staph. and Strep species. What does S. aureus bind to to cause this ?
Platelet associated Von Willebrand Factor
Mannitol Salt +
What is this ?
What are the two major species of CoNS ?
Coagulase - but Catalase +
S. Abiothrophia, formerly called Nutritionally Variant Strep (NVS) must be cultured within 48 hrs with what factors to remain viable ?
L-cysteine and Pyridoxine (B6)
Where in body is S. Abiotrophia a normal fluora ?
URT , Urogenital and GI
Describe the presentation of S. Abiotrophia in IE
Seen in 5%
Indolent (slow moving)
Seen in cases with pre-existing heart disease ( NVE Sub-acute onset)
PRONE TO EMBOLI AND RELAPSE
Higher mortality and morbidity than others
Who often presents with Group D Strep (enterococcus) ?
Older males who have had Urogenital manipulation
Younger women after obstetrics
Why are enterococcus difficult to treat ?
Lab Testing for Group D Strep
6.5% NaCl growth
Bile Esculin +
What two strep species are PYR + ?
Enterococcus (Group D)--> Look for GI issues
S. pyogenes --> Look for rheumatic fever
S. mutans is associated with what portion of the body ?
Mouth. Forms cavities in teeth
S. Mutans is not Group D but is positive for what lab indicator ?
growth on Bile Esculin
S. bovis is also known as
S.bovis is Group D, growing on Bile Esculin. however, it will not grow on...
What should you always check for if you have isolated S.bovis from a heart valve ?
Colon cancer or GI lesion !!! (vis versa also0
NF of the GI tract but is released with damage to GI tract.
HACEK grow on ....
Supplemented Chocolate Agar with supplemented CO2
May also show granular growth in broth
Describe the thrombi associated with HACEK organisms
Large friable lesion
Throw off frequent emboli
Often develop HCF
Often need valve replacement
Aggregatibacter (Actinomyces and aphrophilus)
Growth on what agar can differentiate H. Parainfluenzae from influenzae ?
Blood agar ( H. influenzae only shows up on Chocolate agar)
H. Parainfluenzae is a normal fluora where ?
How long do you need to keep cultures of H. Parainfluenzae ?
Is H. Parainfluenzae Acute or Subacute onset ?
Subacute (like all HACEK) , usually occures on previously damaged valves with underlying valvular disease.
What species is the most common infectious agent of the HACEK's ?
Aggregatibacter is associated with what portion of the body and how long does it take for infection to show ?
Often seen in periodontal disease.
What does Aggregatibacter produce that can cause significant mortality ?
Significant Embolization !!
Cardiobacterium hominus assoiciated IE usually occurs how many months post initial infection ?
Classic characteristics of Cardiobacterium hominus include
Characterized by large vegetations, large vessel emboli
What will you/ smell on agar that Eikenella is growing on ?
Pitting of the agar
Smell Bleach !
Who do you most often see Eikenella IE in ?
IV drug users (IVDU)
People who get bit by other people a lot
Which presentation is more likely to have PMN's : Acute or subacute ?
Which presentation is more likely to have fibroblasts and evidence of repair?
Subacute . Slow onset--> more time for repair
Duke Criteria for Definite IE
2 major criteria
1 major, 3 minor
5 minor criteria
Duke Criteria for Possible IE
1 major and 1 minor
Major Criteria for Duke Scale
1.Positive Blood Culture
Typical microorganism for IE from 2 separate
Blood cultures drawn more than 12 hours apart
All of 3 or majority of > 4 separate blood
cultures, with first and last specimens drawn at
least 1 hour apart
Single positive blood culture for Coxiella burnetii
or antiphase I IgG antibody titer >1:800
2.Evidence of endocardial involvement
How many blood culture sets are taken ? How are they done chronologically ?
3 (each consisting of two veinipunctures)
Acute: 15 mins apart
Subacute: 24 hrs apart
10 ml of blood:
Inoculate rich liquid medium
Subculture days 1&3
Hold at least 3 weeks
Some organisms require 4 weeks
DFA staining of valvular tissue will help to identify which pathogens
What technique is becoming the most effective for identifying organisms as costs for this test go down ?
Positive Endocardial involvement (Major criteria) includes :
1.Positive echocardiogram for IE
A. Oscillating intracardiac mass on valve or
supporting structures or in the path of regurgitant
jets or on iatrogenic devices in the absence of
an alternative anatomic explanation
C.New partial dehiscence of prosthetic valve
2.New valvular regurgitation
Minor Criteria Include
predisposing heart condition or intravenous drug use
temperature > 38.0° C (100.4° F)
major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial hemorrhage, conjunctival hemorrhages, and Janeway lesions
glomerulonephritis, Osler's nodes, Roth spots, and rheumatoid factor
positive blood culture but does not meet a major criterion as noted above¹ or serological evidence of active infection with organism consistent with IE
consistent with IE but do not meet a major criterion as noted above
Macular, blanching, nonpainful, erythematous lesions on palms and soles
Bacteria, neutrophilic infiltration
Necrosis, subcutaneous hemorrhage due to septic emboli
Nonblanching, linear reddish-brown lesions found under the nail bed
INDICATIVE OF ENDOCARDITIS !
Arterial emboli and ischemia of digits distal to a mycotic aneurysm
Aneurysm forms n the artery
Painful, violaceous nodules found in pulp
of fingers and toes, more often in
subacute cases of IE
Immune complexes in dermal plexus
Lesions of the retina