Microbiology Infective Endocarditis and Bacteraemia

Question 1

Definition

Answer 1

• 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.

Question 2

Epidemiology: prevalence

Answer 2

2-6 per 100,000 population per year.

M=F

Question 3

Epi: Prognosis

Answer 3

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

Question 4

Epi Risk Factors

Answer 4

• 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.

Question 5

Epi: Four categories

Answer 5

• Native valve infective endocarditis
• Prosthetic valve infective endocarditis
• IVDU – associated endocarditis
• Nosocomial infective endocarditis

Question 6

Native valve infective endocarditis

Answer 6

• Congenital hear disease (high to lower pressure gradients greatest risk)
• Rheumatic Heart Disease
• Mitral valve prolapse
• Degenerative valve lesions

Question 7

Native valve infective endocarditis organisms involved

Answer 7

Typically are viridans streptococci (oral flora) – streptococcus sanguis.

Question 8

Prosthetic Valve Endocarditis

Answer 8

1-5% of cases
Early (within first 2 months after surgery) or late
Coagulase negative staphylococci predominate

Question 9

IVDU – associated endocarditis

Answer 9

Median age 30 (M>F)
Right sided infection more common → because injection into venous system
Tricuspid 50%; Aortic 25%; Mitral 20%

Question 10

IVDU – associate endocarditis organisms

Answer 10

Staphylococcus aureus predominates, but other organisms, including fungi, sometimes responsible.

Question 11

Nosocomial infective Endocarditis → Incidence

Answer 11

Increasing Incidence (>10% in recent survey)
>60 years

Question 12

Nosocomial infective Endocarditis → Risks

Answer 12

Often underling cardiac disease
Intravenous lines, invasive procedures
Increasing right sided IE due to CVP lines and pulmonary artery catheters

Question 13

Nosocomial infective Endocarditis → Pathogenesis

Answer 13

1. Heat defect leading to a pressure gradient across valve
2. Fibrin platelet deposition and Bacteraemia
3. Colonized fibrin-platelet deposit
4. Further deposition of thrombus
5. Vegetation occurs

Question 14

Nosocomial infective Endocarditis → Infecting organisms

Answer 14

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

Question 15

Nosocomial infective Endocarditis →Immune system

Answer 15

• Inability of the immune system to eradicate the organisms once located on the endocardium

Question 16

Nosocomial infective Endocarditis →Host Factors

Answer 16

• 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.

Question 17

Nosocomial infective Endocarditis → Culture negative

Answer 17

➢ 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.

Question 18

Nosocomial infective Endocarditis → Transient Bacteraemia

Answer 18

➢ Chewing, tooth bruising, dental procedures → worse in the presence of gingivitis
➢ Medical and surgical procedures in non-sterile sites, e.g. urethral catheterisation, endoscopy.

Question 19

Nosocomial infective Endocarditis → Clinical Syndrome

Answer 19

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)

Question 20

Nosocomial infective Endocarditis → Diagnosis

Answer 20

Pathological criteria

Clinical criteria

Question 21

Nosocomial infective Endocarditis →Pathological criteria

Answer 21

Microorganisms: demonstrated by cultre or histology in a vegetation, or in a vegetation that has embolised, or in an intracardiac abscess.

Question 22

Nosocomial infective Endocarditis →Pathological lesions

Answer 22

Vegetation or intra-cardiac abscess present, confirmed by histology showing active endocarditis.

Question 23

Nosocomial infective Endocarditis →Possible Infective Endocarditis

Answer 23

Findings consistent with IE that fall short of “Definite” but are not rejected

Question 24

Nosocomial infective Endocarditis → Rejected

Answer 24

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.

Question 25

Nosocomial infective Endocarditis →Clinical Criteria – Major criteria

Answer 25

1. Possible blood culture
   ➢ Typical organisms for IE from 2 separate blood cultures
   ➢ Persistently positive blood cultures
2. Evidence of endocardial involvement

Question 26

Nosocomial infective Endocarditis → Evidence of endocardial involvement

Answer 26

Positive echocardiogram
➢	Vegetation’s
➢	Abscess
➢	New partial dehiscence of prosthetic valve
➢	New valvular regurgitation

Question 27

Minor Criteria

Answer 27

➢	Predisposition – heart conditions/IVDA
➢	Fever >/=38oc
➢	Vascular phenomena
➢	Immunological phenomena
➢	Microbiological evidence
➢	Echocardiogram

Question 28

Vascular Phenomena

Answer 28

Major arterial emboli, septic pulmonary infarcts, intracranial haemorrhage, Janeway lesions

Question 29

Immunological phenoma

Answer 29

Glomerulonephritis, Oslers nodes, Roth spots, Rheumatoid factor

Question 30

Microbiological evidence

Answer 30

Positive blood culture but not meeting major criteria opposite

Question 31

Echocardiogram

Answer 31

Consistent with IE but not meeting major criteria opposite

Question 32

Complications

Answer 32

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

Question 33

Treatment Principles

Answer 33

Diagnosis with microbiobial confirmation

Antibiotics

Question 34

Q Fever

Answer 34

tetracyclines, co-trimoxazole
➢ Year therapy
➢ Valve replacement

Question 35

Chlamydiae

Answer 35

Tetracyclines