M13: Microbiology of Endocarditis Flashcards
What is the mortality rate of IE if untreated?
Nearly 100%
40-60% of IE cases are caused by what?
Streptococci
20-40% of IE cases are caused by what?
Staphylococci
What are HACEK organisms involved in IE?
- Haemophilus
- Aggregatibacter
- Cardiobacterium
- Eikenella
- Kingella
What is acute IE?
What types of infections do they produce?
- Rapidly destructive & frequent infection on previously normal heart valve
- Acute tend to produce necrotising, ulcerative, invasive infections
What bacteria cause acute IE?
- Staph aureus
- Enterococci
- Strep pneumoniae
What is subacute IE?
- Indolent, lower virulence organisms on previously abnormal or deformed valves
- Subacute are less destructive and vegetations show evidence of healing
List some risk factors of IE (4)
- Ageing population
- Degenerative heart disease - Intravenous drug use
- Rheumatic heart disease
IE Pathogenesis
- Usually affects a heart valve but can involve a septal defect or mural endocardium in a left ventricular aneurysm
- Can also complicate cardiac abnormalities
What are vegetations?
Vegetations are the characteristic lesions occurring in endocarditis They mainly occur on valve leaflets and when blood flows from a high to a low pressure chamber
What is the Septum
Partition between left and right sides of the heart
What is a ventricular aneurysm
A balloon-like swelling in the wall of the heart
What are the different types of IE?
- Affecting previously normal valve
- Affecting previously abnormal native valve
- Affecting prosthetic valves
- Abnormal native valve
- Iatrogenic (a condition resulting from treatment)
What are the virulence factors for oral streptococcal in IE? (3)
- Ability to bind to fibronectin
- Production of extra-cellular polysaccharide
- Ability to bind to platelets
What percentage of IE involve prosthetic valves?
20%
