Microbiology Infective Endocarditis and Bacteraemia Flashcards Preview

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Flashcards in Microbiology Infective Endocarditis and Bacteraemia Deck (35):
1

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.

2

Epidemiology: prevalence

2-6 per 100,000 population per year.
M=F

3

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

4

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.

5

Epi: Four categories

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

6

Native valve infective endocarditis

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

7

Native valve infective endocarditis organisms involved

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

8

Prosthetic Valve Endocarditis

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

9

IVDU – associated endocarditis

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

10

IVDU – associate endocarditis organisms

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

11

Nosocomial infective Endocarditis → Incidence

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

12

Nosocomial infective Endocarditis → Risks

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

13

Nosocomial infective Endocarditis → Pathogenesis

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

14

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

15

Nosocomial infective Endocarditis →Immune system

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

16

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.

17

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.

18

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.

19

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)

20

Nosocomial infective Endocarditis → Diagnosis

Pathological criteria
Clinical criteria

21

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.

22

Nosocomial infective Endocarditis →Pathological lesions

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

23

Nosocomial infective Endocarditis →Possible Infective Endocarditis

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

24

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.

25

Nosocomial infective Endocarditis →Clinical Criteria – Major criteria

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

26

Nosocomial infective Endocarditis → Evidence of endocardial involvement

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

27

Minor Criteria

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

28

Vascular Phenomena

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

29

Immunological phenoma

Glomerulonephritis, Oslers nodes, Roth spots, Rheumatoid factor

30

Microbiological evidence

Positive blood culture but not meeting major criteria opposite

31

Echocardiogram

Consistent with IE but not meeting major criteria opposite

32

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

33

Treatment Principles

Diagnosis with microbiobial confirmation
Antibiotics

34

Q Fever

tetracyclines, co-trimoxazole
➢ Year therapy
➢ Valve replacement

35

Chlamydiae

Tetracyclines

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