Microbiology Infective Endocarditis and Bacteraemia Flashcards
Definition
- Bacterial (or fungal) infection of a heart valve or area of endocardium
- Clinical presentation traditionally classified as either acute of sub-acute
- Particular constellations of clinical signs and investigation results (diagnostic criteria) are required in order to make the diagnosis.
Epidemiology: prevalence
2-6 per 100,000 population per year.
M=F
Epi: Prognosis
Invariably lethal pre-antibiotics, it has still not gone away and may be on the increased in some categories of patients.
Still significant mortality (20%) and morbidity
Epi Risk Factors
- Risk factors and infecting organisms have changed over time, e.g. rheumatic fever was prime risk factor in up to 75% of cases in the pre-antibiotic era, but rare now.
- Different organisms associated with different risk factors.
Epi: Four categories
- Native valve infective endocarditis
- Prosthetic valve infective endocarditis
- IVDU – associated endocarditis
- Nosocomial infective endocarditis
Native valve infective endocarditis
- Congenital hear disease (high to lower pressure gradients greatest risk)
- Rheumatic Heart Disease
- Mitral valve prolapse
- Degenerative valve lesions
Native valve infective endocarditis organisms involved
Typically are viridans streptococci (oral flora) – streptococcus sanguis.
Prosthetic Valve Endocarditis
1-5% of cases
Early (within first 2 months after surgery) or late
Coagulase negative staphylococci predominate
IVDU – associated endocarditis
Median age 30 (M>F)
Right sided infection more common → because injection into venous system
Tricuspid 50%; Aortic 25%; Mitral 20%
IVDU – associate endocarditis organisms
Staphylococcus aureus predominates, but other organisms, including fungi, sometimes responsible.
Nosocomial infective Endocarditis → Incidence
Increasing Incidence (>10% in recent survey) >60 years
Nosocomial infective Endocarditis → Risks
Often underling cardiac disease
Intravenous lines, invasive procedures
Increasing right sided IE due to CVP lines and pulmonary artery catheters
Nosocomial infective Endocarditis → Pathogenesis
- Heat defect leading to a pressure gradient across valve
- Fibrin platelet deposition and Bacteraemia
- Colonized fibrin-platelet deposit
- Further deposition of thrombus
- Vegetation occurs
Nosocomial infective Endocarditis → Infecting organisms
Typical:
• 80% gram +ve – various fibrin binding proteins = sticky
• Ability to adhere and colonise damaged valves
• Staphylococcus aureus, Streptococcus sp,.
• Enterococci together are responsible for >80% of cases.
• Gram -ve
Nosocomial infective Endocarditis →Immune system
• Inability of the immune system to eradicate the organisms once located on the endocardium
Nosocomial infective Endocarditis →Host Factors
- Pre-existing lesions of the layer of endothelial cells covering the valve or endovascular surface
- Congenital cardiac abnormalities causing turbulent blood flows
- Rheumatic fever resulting in valvular damage
- Prosthetic valves
- Sclerotic valves in elderly patients
- Invasive procedures/intravascular lines.
Nosocomial infective Endocarditis → Culture negative
➢ Q fever (Coxiella burnetti)
➢ Chlamydiae
➢ Brucella spp.
Therefore, if the diagnosis is suspected, a serum sample on admission and another 4 weeks later may be invaluable.
Nosocomial infective Endocarditis → Transient Bacteraemia
➢ Chewing, tooth bruising, dental procedures → worse in the presence of gingivitis
➢ Medical and surgical procedures in non-sterile sites, e.g. urethral catheterisation, endoscopy.
Nosocomial infective Endocarditis → Clinical Syndrome
Acute & Subacute
➢ Malaise (95%), pyrexia (90%), arthralgia (25%)
➢ Cardiac murmurs (90%), cardiac failure (5)
➢ Osler’s nodes (15%), Janeway lesions (5%)
➢ Splenomegaly (40%), cerebral emboli (20%)
➢ Haematuria (705)
Nosocomial infective Endocarditis → Diagnosis
Pathological criteria
Clinical criteria
Nosocomial infective Endocarditis →Pathological criteria
Microorganisms: demonstrated by cultre or histology in a vegetation, or in a vegetation that has embolised, or in an intracardiac abscess.
Nosocomial infective Endocarditis →Pathological lesions
Vegetation or intra-cardiac abscess present, confirmed by histology showing active endocarditis.
Nosocomial infective Endocarditis →Possible Infective Endocarditis
Findings consistent with IE that fall short of “Definite” but are not rejected
Nosocomial infective Endocarditis → Rejected
Film alternative diagnosis for manifestations of endocarditis, or resolution of manifestations with antibiotic therapy of 4 days or less. Or no pathological evidence of IE at surgery or autopsy after antibiotic therapy for 4 days or less.
Nosocomial infective Endocarditis →Clinical Criteria – Major criteria
- Possible blood culture
➢ Typical organisms for IE from 2 separate blood cultures
➢ Persistently positive blood cultures - Evidence of endocardial involvement
Nosocomial infective Endocarditis → Evidence of endocardial involvement
Positive echocardiogram ➢ Vegetation’s ➢ Abscess ➢ New partial dehiscence of prosthetic valve ➢ New valvular regurgitation
Minor Criteria
➢ Predisposition – heart conditions/IVDA ➢ Fever >/=38oc ➢ Vascular phenomena ➢ Immunological phenomena ➢ Microbiological evidence ➢ Echocardiogram
Vascular Phenomena
Major arterial emboli, septic pulmonary infarcts, intracranial haemorrhage, Janeway lesions
Immunological phenoma
Glomerulonephritis, Oslers nodes, Roth spots, Rheumatoid factor
Microbiological evidence
Positive blood culture but not meeting major criteria opposite
Echocardiogram
Consistent with IE but not meeting major criteria opposite
Complications
Valvular destruction leading to cardiac failure Surgery if indicated: ➢ Extensive damage to valve ➢ Infection of prosthetic valve ➢ Worsening renal failure ➢ Persistent infection but dailure to culture organisms= ➢ Embolisation ➢ Large vegetation’s Embolization – cerebral, pulmonary Acute renal failure – secondary to IE or to treatment – aminoglycosides.glycopeptides Mycotic aneurysms Death
Treatment Principles
Diagnosis with microbiobial confirmation
Antibiotics
Q Fever
tetracyclines, co-trimoxazole
➢ Year therapy
➢ Valve replacement
Chlamydiae
Tetracyclines
