๐ Key Information Summary
- Infective endocarditis (IE) carries a mortality of 15โ30% even with optimal treatment; early diagnosis and multidisciplinary management are critical.
- The modified Duke criteria remain the gold standard for diagnosis, classifying cases as definite or possible IE based on pathological, major, and minor criteria.
- Three sets of blood cultures from separate venepuncture sites must be obtained before empirical antibiotics; each set includes an aerobic and anaerobic bottle.
- Transthoracic echocardiography (TTE) is the first-line imaging; transoesophageal echocardiography (TEE) is mandatory if TTE is negative, if prosthetic valve IE is suspected, or if complications are suspected.
- Staphylococcus aureus is the most common cause in Australia (โ30% of cases), including community-associated methicillin-resistant S. aureus (CA-MRSA) in Aboriginal and Torres Strait Islander communities.
- Empirical therapy for native valve IE is flucloxacillin + gentamicin; prosthetic valve IE requires vancomycin + gentamicin + rifampicin pending culture results.
- Antibiotic durations are typically 4โ6 weeks for native valve IE and โฅ6 weeks for prosthetic valve IE, administered IV for the full course.
- Surgical indications include heart failure from valvular dysfunction, uncontrolled infection (abscess, fistula, persistently positive cultures), recurrent embolic events with large vegetations, and prosthetic valve IE with complications.
- Major complications include perivalvular abscess, conduction abnormalities (new heart block warrants urgent TEE), embolic stroke, mycotic aneurysm, and renal failure.
- Antibiotic prophylaxis is recommended before dental and certain invasive procedures in patients with prosthetic valves, previous IE, or congenital heart disease with residual defects.
- Aboriginal and Torres Strait Islander peoples have a significantly higher incidence of IE due to rheumatic heart disease, higher rates of CA-MRSA, and barriers to healthcare access in remote communities.
- All cases should be discussed with an endocarditis team comprising cardiology, cardiothoracic surgery, infectious diseases, and microbiology at the earliest opportunity.
Introduction & Australian Epidemiology
Infective endocarditis (IE) is a life-threatening infection of the endocardial surface of the heart, most commonly involving the heart valves. Despite advances in diagnosis and treatment, IE remains associated with significant morbidity and mortality, with in-hospital mortality rates of 15โ30% and 5-year mortality approaching 40%.
In Australia, the estimated incidence of IE is approximately 3โ7 per 100,000 population per year, though this is likely an underestimate. The epidemiology has shifted over recent decades: Staphylococcus aureus has replaced viridans group streptococci as the leading cause, healthcare-associated IE has increased, and there is a persistent burden among people who inject drugs (PWID) and those with rheumatic heart disease (RHD).
Australian data: Aboriginal and Torres Strait Islander Australians experience IE at rates 5โ10 times higher than the non-Indigenous population, driven by the high prevalence of RHD, CA-MRSA, skin and soft tissue infections, and barriers to healthcare access in remote and very remote regions. The AIHW reports that RHD-related IE accounts for a disproportionate share of hospitalisations in Northern Territory and Far North Queensland.
Key Australian trends include:
- Healthcare-associated IE: Increasing proportion of cases related to indwelling intravascular devices, haemodialysis access, and nosocomial bacteraemia.
- Injecting drug use: Right-sided (tricuspid valve) IE is the predominant pattern, most commonly caused by S. aureus.
- Prosthetic valve IE: Accounts for 10โ30% of all IE cases; early (within 12 months of surgery) and late (>12 months) forms have distinct microbiological profiles.
- Rheumatic heart disease: Remains a significant risk factor in Indigenous Australians, particularly in the Northern Territory and Western Australia.
- Ageing population: Degenerative valvular disease in older Australians increases susceptibility, with a median age at diagnosis now exceeding 60 years.
| Risk Factor | Comment |
|---|---|
| Prosthetic heart valve | Highest risk; 1โ6% lifetime incidence |
| Previous infective endocarditis | Recurrence rate 2โ6% per patient-year |
| Rheumatic heart disease | Significant burden in ATSI populations |
| Congenital heart disease | Particularly unrepaired cyanotic lesions |
| Injecting drug use | Right-sided IE, typically S. aureus |
| Indwelling intravascular devices | Central lines, ports, pacemakers |
| Haemodialysis | AV fistula or catheter-related |
| Immunosuppression | Transplant recipients, HIV (low CD4) |
| Poor dental health | Periodontitis as portal of entry for oral streptococci |
Diagnosis
Modified Duke Criteria
The modified Duke criteria remain the cornerstone of IE diagnosis. They stratify patients into definite, possible, or rejected IE based on major and minor clinical criteria. Pathological criteria (histology or culture of excised tissue or embolic material) provide definitive diagnosis.
| Criterion Type | Criteria |
|---|---|
| Major โ Blood cultures | 1. Typical organism from โฅ2 separate blood cultures: S. aureus, viridans group streptococci, S. gallolyticus (formerly S. bovis), HACEK group, or community-acquired Enterococcus spp. with no primary focus 2. Persistently positive blood cultures: โฅ2 positive cultures drawn >12 h apart, or all of 3 or majority of โฅ4 separate cultures positive |
| Major โ Endocardial involvement | 1. Echocardiographic findings: oscillating intracardiac mass on a valve or supporting structure, in the path of regurgitant jets, or on implanted material (in the absence of alternative explanation); perivalvular abscess; new partial dehiscence of a prosthetic valve 2. New valvular regurgitation (worsening or changing of pre-existing murmur not sufficient) |
| Minor criteria | 1. Predisposing heart condition or intravenous drug use 2. Fever โฅ38ยฐC 3. Vascular phenomena: major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial haemorrhage, conjunctival haemorrhage, Janeway lesions 4. Immunological phenomena: glomerulonephritis, Osler nodes, Roth spots, positive rheumatoid factor 5. Microbiological evidence not meeting major criteria (single positive culture of an atypical organism, or serological evidence of active infection) |
Definite IE: 2 major criteria, OR 1 major + 3 minor, OR 5 minor criteria. Possible IE: 1 major + 1 minor, OR 3 minor criteria. Rejected: Firm alternative diagnosis, resolution of symptoms with โค4 days of antibiotics, or no pathological evidence at surgery/autopsy with โค4 days of antibiotics.
Blood Culture Protocol
Blood cultures are the single most important microbiological investigation and must be collected before any antibiotic therapy is initiated.
1
Collect 3 sets of blood cultures
From 3 separate venepuncture sites (e.g., both antecubital fossae + one peripheral site). Each set = 1 aerobic + 1 anaerobic bottle (total 6 bottles).
2
Volume
Adults: 20โ30 mL per set (10 mL per bottle). Paediatric: volume based on weight; consult local microbiology (typically 1โ5 mL per bottle).
3
Timing
Obtain all sets within 1โ2 hours if possible. No need to wait for fever spikes (continuous bacteraemia). Stagger only if logistically necessary.
4
Transport & processing
Label clearly with time and site. Send immediately to microbiology. Extended incubation (14โ21 days) may be requested for suspected HACEK or culture-negative IE.
Do not delay antibiotics in a haemodynamically unstable patient to obtain cultures. Empiric therapy must begin immediately after blood cultures are drawn in septic or haemodynamically compromised patients.
Echocardiography
| Modality | Sensitivity | Indications | Limitations |
|---|---|---|---|
| Transthoracic echocardiography (TTE) | 50โ60% for vegetations overall; ~90% for native valve vegetations >5 mm | First-line investigation in all suspected IE | Poor sensitivity for prosthetic valve IE, small vegetations (<5 mm), perivalvular abscess; limited by body habitus and lung disease |
| Transoesophageal echocardiography (TEE) | 90โ95% overall; superior for prosthetic valve and complications | Negative or inconclusive TTE with high clinical suspicion; suspected prosthetic valve IE; suspected complications (abscess, fistula); S. aureus bacteraemia; persistently positive blood cultures | Semi-invasive; requires sedation or GA; small risk of oesophageal perforation |
Australian access: TTE is widely available across metropolitan and regional centres. TEE availability is more limited in rural and remote areas; transfer to a tertiary centre with cardiothoracic and cardiac imaging services (e.g., Royal Melbourne, Royal Adelaide, Royal Brisbane, Royal Perth) may be required.
Additional Imaging
- 18F-FDG PET/CT: Increasingly used for prosthetic valve IE diagnosis (added as a major criterion in the 2023 ESC guidelines) and detection of embolic events. Useful for diagnosis of prosthetic valve IE when echo is inconclusive. Availability is limited to major metropolitan centres.
- Gallium-67 or labelled white cell scanning: May be considered for cardiac device infection where PET/CT is unavailable.
- CT brain (ยฑ CT angiography): Recommended in all patients with S. aureus IE to detect silent embolic events or mycotic aneurysms.
- CT chest: Septic pulmonary emboli (especially in right-sided IE); may show peripheral wedge-shaped nodular opacities with cavitation.
- CT abdomen/pelvis: Assess for splenic infarction, renal infarction, mycotic aneurysms, spondylodiscitis.
- MRI brain: Superior to CT for detection of cerebral microabscesses, septic emboli, and mycotic aneurysms. Perform if neurological symptoms or signs are present.
- Cardiac CT (ECG-gated): Valuable for assessing perivalvular anatomy, abscess, and pseudoaneurysm, especially in prosthetic valve IE where echocardiographic windows are poor.
Microbiology & Antibiotic Therapy
Common Causative Organisms
| Organism | Frequency | Typical Setting | Key Points |
|---|---|---|---|
| Staphylococcus aureus | 30โ40% | Healthcare-associated, PWID, community | Most common cause overall; aggressive course; high embolic risk. MRSA prevalent in ATSI communities and hospital-acquired cases. |
| Viridans group streptococci | 15โ25% | Community-acquired, dental source | Oral flora; usually penicillin-susceptible; associated with subacute presentation. Includes S. sanguinis, S. mutans, S. mitis/oralis. |
| Streptococcus gallolyticus (formerly S. bovis) | 5โ10% | GI source | Strong association with colonic neoplasia; colonoscopy is mandatory in all cases. |
| Enterococcus spp. | 5โ10% | Healthcare-associated, GU source, elderly | Usually E. faecalis; often requires combination therapy (ampicillin + gentamicin or ceftriaxone). E. faecium may be ampicillin-resistant โ vancomycin required. |
| HACEK group | 2โ5% | Community-acquired, oral source | Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella. Slow-growing; extended incubation needed. Usually ฮฒ-lactamase negative โ ceftriaxone is the treatment of choice. |
| Coagulase-negative staphylococci | 5โ10% | Prosthetic valve IE (especially S. epidermidis) | Most common cause of prosthetic valve IE; often methicillin-resistant. Rifampicin is added for prosthetic valve infections. |
| Fungi (Candida, Aspergillus) | <2% | Prosthetic valve, immunocompromised, PWID | Very high mortality (>50%); almost always requires surgical intervention. Blood cultures often negative โ consider fungal serology and beta-D-glucan. |
Culture-Negative Infective Endocarditis
Culture-negative IE accounts for 5โ15% of cases in Australia. Causes include prior antibiotic exposure (most common), fastidious organisms, and non-infectious mimics.
- Prior antibiotic use: Most common cause; may need to cease antibiotics and re-culture after a washout period if clinically safe.
- Fastidious organisms: HACEK group (extend incubation to 14โ21 days), Coxiella burnetii (Q fever โ serology), Bartonella spp. (serology and PCR), Tropheryma whipplei (PCR, small bowel biopsy), Brucella spp. (serology, extended incubation).
- Q fever endocarditis: Australia is endemic for Q fever; Coxiella burnetii serology (phase I IgG >1:800) should be sent in all culture-negative IE cases. Treatment is doxycycline + hydroxychloroquine.
- Molecular diagnostics: 16S rRNA PCR on excised valve tissue or embolic material; broad-range PCR on blood may assist.
Empirical Antibiotic Therapy
All regimens below are for adult patients unless otherwise specified. Adjust for renal function, allergy, and local resistance patterns. Discuss with infectious diseases and microbiology. All IE antibiotic therapy requires prolonged IV administration โ ensure IV access (PICC line preferred) and arrange inpatient or Hospital in the Home (HITH) if appropriate.
Flucloxacillin
Staphcillinยฎ ยท ฮฒ-lactam (isoxazolyl penicillin)
Adult dose
2 g IV every 4 hours (12 g/day) for native valve S. aureus IE; 6 weeks duration
Paediatric dose
50 mg/kg (max 2 g) IV every 4โ6 hours
Renal adjustment
No adjustment required (hepatically metabolised)
PBS status
โ PBS General Benefit
Vancomycin
Vancocinยฎ ยท Glycopeptide
Adult dose
15โ20 mg/kg IV every 8โ12 hours (AUC-guided dosing, target AUC/MIC 400โ600); for MRSA IE, prosthetic valve IE, or penicillin allergy
Paediatric dose
15 mg/kg IV every 6 hours (adjust per therapeutic drug monitoring)
Renal adjustment
Reduce dose and extend interval based on trough levels and renal function; consult pharmacy
PBS status
โ PBS General Benefit
Gentamicin
Cidomycinยฎ ยท Aminoglycoside
Adult dose
1 mg/kg IV every 8 hours (dose for staphylococcal synergy); 2 weeks for native valve; 6 weeks for prosthetic valve. TDM required โ once-daily dosing (5โ7 mg/kg) not standard for endocarditis synergy.
Renal adjustment
Dose per actual body weight; adjust interval based on serum levels and eGFR
PBS status
โ PBS General Benefit
Benzylpenicillin
Crystapenยฎ ยท Natural penicillin
Adult dose
1.8โ2.4 g IV every 4 hours for penicillin-susceptible viridans group streptococcal IE; 4 weeks duration
Paediatric dose
50 mg/kg (max 2.4 g) IV every 4โ6 hours
Renal adjustment
Reduce dose if eGFR <30 mL/min โ consult renal/pharmacy
PBS status
โ PBS General Benefit
Ampicillin
Penbritinยฎ ยท Aminopenicillin
Adult dose
2 g IV every 4 hours for enterococcal IE (with gentamicin); 4โ6 weeks duration
Renal adjustment
Reduce dose if eGFR <30 mL/min
PBS status
โ PBS General Benefit
Ceftriaxone
Rocephinยฎ ยท Third-generation cephalosporin
Adult dose
2 g IV once daily for HACEK endocarditis (4 weeks) or as penicillin-susceptible streptococcal IE monotherapy (4 weeks); also used in E. faecalis synergy with ampicillin (Ampicillin + Ceftriaxone regimen)
Renal adjustment
No adjustment required (dual elimination)
PBS status
โ PBS General Benefit
Rifampicin
Rifadinยฎ ยท Rifamycin
Adult dose
300โ450 mg PO/IV every 12 hours; used ONLY in prosthetic valve staphylococcal IE as adjunctive therapy (with vancomycin or flucloxacillin + gentamicin) for โฅ6 weeks due to its ability to penetrate biofilm
Key interactions
Potent CYP3A4 inducer โ significant interactions with warfarin, DOACs, antifungals, and many other medications
PBS status
โ PBS General Benefit
Daptomycin
Cubicinยฎ ยท Cyclic lipopeptide
Adult dose
8โ10 mg/kg IV once daily; alternative for MRSA IE when vancomycin is not tolerated or failing; also used for right-sided S. aureus IE and vancomycin-resistant Enterococcus
Renal adjustment
Extend interval to every 48 hours if CrCl <30 mL/min
PBS status
โ PBS Authority Required
Empirical Regimens
| Clinical Scenario | Empirical Regimen | Duration |
|---|---|---|
| Native valve โ community-acquired | Flucloxacillin 2 g IV 4-hourly + Gentamicin 1 mg/kg IV 8-hourly | Pending culture; adjust to targeted regimen |
| Native valve โ suspected MRSA or penicillin allergy (anaphylaxis) | Vancomycin 15โ20 mg/kg IV 8โ12-hourly (AUC-guided) | Pending culture; may add gentamicin for synergy |
| Prosthetic valve IE (any timing) | Vancomycin 15โ20 mg/kg IV 8โ12-hourly + Gentamicin 1 mg/kg IV 8-hourly + Rifampicin 300โ450 mg PO/IV 12-hourly | Pending culture; โฅ6 weeks for staphylococcal PVE |
| Suspected enterococcal IE | Ampicillin 2 g IV 4-hourly + Gentamicin 1 mg/kg IV 8-hourly | 4โ6 weeks |
| Injecting drug use (right-sided) | Flucloxacillin 2 g IV 4-hourly ยฑ Gentamicin 1 mg/kg IV 8-hourly | 2 weeks (if S. aureus MSSA, right-sided only, no complications โ short-course possible); otherwise 4โ6 weeks |
Directed Therapy by Organism โ Summary
| Organism | First-Line Regimen | Duration (Native Valve) | Duration (Prosthetic Valve) |
|---|---|---|---|
| S. aureus (MSSA) | Flucloxacillin 2 g IV 4-hourly ยฑ Gentamicin 1 mg/kg IV 8-hourly (first 2 weeks for synergy) | 4โ6 weeks | โฅ6 weeks + rifampicin |
| S. aureus (MRSA) | Vancomycin (AUC-guided) ยฑ Gentamicin; or Daptomycin 8โ10 mg/kg IV daily | 6 weeks | โฅ6 weeks + rifampicin |
| Viridans streptococci (Pen MIC โค0.12 mg/L) | Benzylpenicillin 1.8โ2.4 g IV 4-hourly ยฑ Gentamicin (first 2 weeks) | 4 weeks | 6 weeks |
| Viridans streptococci (Pen MIC 0.25โ2 mg/L) | Benzylpenicillin 2.4 g IV 4-hourly + Gentamicin (2 weeks) | 4 weeks | 6 weeks |
| E. faecalis (Pen-susceptible) | Ampicillin 2 g IV 4-hourly + Gentamicin 1 mg/kg IV 8-hourly; OR Ampicillin + Ceftriaxone (if aminoglycoside contraindicated) | 4โ6 weeks | โฅ6 weeks |
| E. faecium (ampicillin-resistant) | Vancomycin + Gentamicin; consult ID for linezolid or daptomycin if VRE | 6 weeks | โฅ6 weeks |
| HACEK group | Ceftriaxone 2 g IV once daily | 4 weeks | 6 weeks |
| CoNS (prosthetic valve) | Vancomycin + Rifampicin 300 mg PO 12-hourly + Gentamicin (first 2 weeks) | N/A | โฅ6 weeks |
| Coxiella burnetii | Doxycycline 100 mg PO BD + Hydroxychloroquine 200 mg PO TDS | โฅ18 months (lifelong in some cases) | โฅ18 months |
| Candida spp. | Liposomal amphotericin B ยฑ flucytosine; step down to fluconazole (lifelong suppressive if not surgically excised) | Lifelong suppression if valve retained | Lifelong suppression |
Outpatient Parenteral Antibiotic Therapy (OPAT) / Hospital in the Home (HITH): Many Australian centres offer HITH for the latter portion of IV antibiotic courses for stable IE patients. Criteria typically include haemodynamic stability, absence of complications, reliable IV access (PICC line), and patient ability to self-care or carer availability. Discuss early with HITH services to facilitate transition.
Surgical Indications
Surgery is required in approximately 40โ50% of IE cases during the index admission. An endocarditis team (cardiologist, cardiothoracic surgeon, infectious diseases physician, microbiologist, neurologist, and imaging specialist) should discuss all cases early. Urgent surgery (within 48 hours) may be lifesaving.
Do not delay surgery for prolonged antibiotic courses in patients with clear surgical indications. Evidence shows that surgery during active infection, when indicated, improves outcomes compared with conservative management alone.
Indications for Surgery
Emergency / Urgent
Heart Failure
Acute severe regurgitation (aortic or mitral) causing pulmonary oedema or cardiogenic shock, even if haemodynamically unstable. Surgery within 24โ48 hours.
Setting: Emergency surgery โ ICU, tertiary centre
Emergency / Urgent
Uncontrolled Infection
Perivalvular abscess, fistula, false aneurysm, enlarging vegetation despite appropriate antibiotics, persistently positive blood cultures (>7 days) on appropriate therapy, or infection caused by resistant organisms or fungi.
Setting: Urgent surgery โ within days of diagnosis
Urgent / Elective
Prevention of Embolic Events
Vegetation >10 mm with prior embolic event; vegetation >15 mm with other risk factors (size increase on therapy, mobility, organism); mobile vegetation >20 mm even without embolism. Especially if involving mitral valve anterior leaflet.
Setting: Semi-urgent โ within 1โ2 weeks
Urgent / Semi-urgent
Prosthetic Valve IE with Complications
Dehiscence, valve obstruction, heart failure, abscess, or fistula. Early PVE has worse outcomes with antibiotics alone. Surgery is more frequently indicated than in native valve IE.
Setting: Urgent โ multidisciplinary planning
Relative Indications for Surgery
- Staphylococcal prosthetic valve IE (frequently requires surgery)
- Fungal IE (almost always requires surgery)
- Left-sided IE with large vegetations (>10 mm) and significant valvular dysfunction
- Conduction abnormalities suggesting perivalvular extension (new AV block)
- Relapse after completion of appropriate antibiotic therapy
- Persistent fever >10 days without alternative explanation
Contraindications to Surgery
- Severe irreversible neurological deficit (discuss with neurology โ moderate stroke may still proceed to surgery after 1โ2 weeks if haemorrhagic transformation excluded)
- Severe comorbidities with unacceptably high operative risk
- Severe septic shock unresponsive to resuscitation (relative)
Australian surgical centres: Cardiac surgery for IE is available at major tertiary centres across all states (e.g., Royal Melbourne, Royal Prince Alfred, Royal Adelaide, Fiona Stanley, Royal Brisbane and Women's Hospital). Patients in rural and remote areas should be discussed with the nearest cardiothoracic unit early for transfer planning.
Complications
Complications of IE are a major driver of morbidity and mortality. They may arise from direct infection spread (local), embolic phenomena (systemic), immune-mediated processes, or treatment toxicity.
Perivalvular Abscess
- Occurs in 10โ40% of native valve IE and up to 60% of prosthetic valve IE.
- Most common in the aortic annulus (mitro-aortic intervalvular fibrosa region).
- Clinical clue: New AV conduction abnormalities (first-degree AV block, bundle branch block, complete heart block), persistent fever on appropriate antibiotics, or persistent bacteraemia.
- Diagnosis: TEE is the investigation of choice (sensitivity >85%). CT cardiac (ECG-gated) is a valuable adjunct. TTE has limited sensitivity for abscess.
- Management: Almost always requires surgical drainage and debridement. Antibiotics alone rarely sufficient. New heart block in the setting of IE should be treated as perivalvular abscess until proven otherwise.
New heart block in IE: If a patient with IE develops new first-degree AV block, bundle branch block, or complete heart block, urgent TEE is mandatory to evaluate for perivalvular abscess. This is a surgical emergency.
Conduction Abnormalities
- New PR prolongation, bundle branch block, or complete heart block occurs in 5โ15% of cases.
- Strongly associated with perivalvular abscess (aortic valve IE > mitral valve IE).
- Any new conduction abnormality mandates urgent TEE and cardiothoracic surgical review.
- Temporary pacing may be required; permanent pacemaker implantation may be needed if conduction does not recover after surgical debridement.
Embolic Events
| Embolic Site | Frequency | Clinical Features | Management |
|---|---|---|---|
| Cerebral (ischaemic stroke) | 15โ25% | Focal neurological deficit; may be clinically silent on imaging in up to 50% of S. aureus IE | CT brain ยฑ MRI; anticoagulation generally NOT recommended for ischaemic stroke in IE; discuss neurology; surgery timing may be delayed 2โ4 weeks if large infarct |
| Cerebral (haemorrhagic) | 3โ5% | Headache, altered consciousness, focal deficit; may occur as complication of anticoagulation or mycotic aneurysm rupture | CT brain urgently; hold anticoagulation; neurosurgical review; contraindication to cardiopulmonary bypass |
| Splenic infarction/abscess | 10โ40% (subclinical) | Left upper quadrant pain, fever; CT shows peripheral wedge defects or abscess | Most resolve with antibiotics; splenic abscess may require percutaneous drainage or splenectomy |
| Renal infarction | 10โ30% | Flank pain, haematuria, rising creatinine | Supportive care; also consider immune-complex glomerulonephritis and drug-induced nephrotoxicity |
| Septic pulmonary emboli | Common in right-sided IE (PWID) | Dyspnoea, pleuritic chest pain, haemoptysis; CT chest shows peripheral nodular infiltrates with cavitation | Antibiotics; rarely requires surgical intervention |
| Spondylodiscitis / Vertebral osteomyelitis | 3โ15% | Back pain, fever; MRI spine is the investigation of choice | Prolonged antibiotic course (โฅ6 weeks total from IE start); may require surgical debridement |
| Peripheral arterial emboli | 5โ15% | Acute limb ischaemia (pain, pallor, pulselessness); may present with Osler nodes, Janeway lesions | Vascular surgery review; embolectomy if critical ischaemia |
Mycotic Aneurysm
- Result from septic emboli lodging in the vasa vasorum or direct arterial wall infection.
- Most common sites: intracranial (especially middle cerebral artery bifurcation), aorta, visceral arteries, and peripheral arteries.
- Diagnosis: CT angiography or MR angiography. Conventional angiography if endovascular intervention planned.
- Management: Prolonged IV antibiotics; surgical or endovascular intervention for rupture, expansion, or failure to respond to medical therapy. Neurosurgical intervention for intracranial mycotic aneurysms (clipping or coiling).
- Aneurysm surveillance: Repeat imaging at intervals to assess for expansion or new aneurysm formation.
Other Complications
- Heart failure: May be acute (valvular regurgitation) or chronic; echocardiographic monitoring is essential.
- Renal failure: Multifactorial โ embolic, immune-complex glomerulonephritis, drug toxicity (vancomycin, gentamicin). Monitor renal function closely.
- Drug fever / hypersensitivity: Diagnosis of exclusion; do not prematurely discontinue antibiotics without infectious diseases input.
Prophylaxis & Prevention
Australian guidelines (aligned with the American Heart Association 2007 update and endorsed by the Cardiac Society of Australia and New Zealand) recommend antibiotic prophylaxis before dental and certain invasive procedures in patients at highest risk of adverse outcomes from IE.
High-Risk Conditions Requiring Prophylaxis
- Prosthetic heart valve or prosthetic material used for valve repair
- Previous infective endocarditis
- Congenital heart disease: unrepaired cyanotic CHD, completely repaired CHD with prosthetic material within the first 6 months, repaired CHD with residual defects at or near the site of a prosthetic patch
- Cardiac transplant recipients who develop valvulopathy
Note: Rheumatic heart disease alone does not require dental prophylaxis under current Australian guidelines. However, given the high burden of RHD in ATSI populations and the association with IE, oral health promotion and regular dental care are strongly recommended in these populations.
Procedures Requiring Prophylaxis
Prophylaxis is recommended for dental procedures involving manipulation of gingival tissue, the periapical region of teeth, or perforation of the oral mucosa. It is also considered for certain respiratory, gastrointestinal, and genitourinary procedures only in the setting of known active infection.
Dental Prophylaxis Regimen
Amoxicillin
First-line dental prophylaxis
Adult dose
2 g PO as a single dose, 30โ60 minutes before procedure
Paediatric dose
50 mg/kg PO (max 2 g) as a single dose, 30โ60 minutes before procedure
PBS status
โ PBS General Benefit
Clindamycin
Alternative for penicillin allergy
Adult dose
600 mg PO as a single dose, 30โ60 minutes before procedure
Paediatric dose
20 mg/kg PO (max 600 mg) as a single dose
PBS status
โ PBS General Benefit
Cefalexin
Alternative (penicillin allergy โ non-anaphylaxis)
Adult dose
2 g PO as a single dose, 30โ60 minutes before procedure
Paediatric dose
50 mg/kg PO (max 2 g) as a single dose
PBS status
โ PBS General Benefit
Non-Dental Invasive Procedures
For respiratory procedures (bronchoscopy, tonsillectomy), GI or GU procedures in the setting of known active infection, administer antibiotics targeting the infecting organism per standard guidelines. Routine prophylaxis for GI and GU procedures in the absence of infection is not recommended.
Intravenous Drug Use โ Counselling & Harm Reduction
- Primary prevention: Needle and syringe programmes (NSP) across all Australian states and territories reduce IE risk from contaminated injection equipment.
- Injecting technique counselling: Avoid injection into the groin or neck veins; skin cleaning before injection; never share equipment.
- Opioid substitution therapy (OST): Methadone and buprenorphine programmes reduce injecting frequency and IE risk.
- Engagement with addiction services: Refer to local drug and alcohol services; non-judgemental, multidisciplinary approach improves outcomes.
- Cardiac monitoring: PWID with persistent febrile illness should have low threshold for echocardiography and blood cultures.
- Recurrence prevention: Patients with a history of IE and ongoing injecting drug use have high recurrence rates (up to 40%); consider supervised OST and harm reduction counselling at every healthcare encounter.
Infection Prevention in Healthcare
- Strict aseptic technique for all intravascular device insertion and maintenance.
- Antimicrobial stewardship to reduce bacteraemia from healthcare-associated infections.
- Dental assessment and treatment prior to elective cardiac surgery and valve replacement.
- Skin preparation and screening for S. aureus nasal carriage prior to cardiac surgery (decolonisation with mupirocin nasal ointment and chlorhexidine washes).
Special Populations
Pregnancy
Preferred antibiotics: Penicillins (benzylpenicillin, amoxicillin, flucloxacillin) and cephalosporins (ceftriaxone) are generally safe. Vancomycin is acceptable when required. Gentamicin carries ototoxicity risk โ use only when essential with TDM.
Avoid: Doxycycline (teratogenic โ except for Q fever endocarditis where benefit may outweigh risk). Fluoroquinolones. Trimethoprim (first trimester โ folate antagonist; avoid near term). Daptomycin โ limited safety data.
Surgery: Cardiac surgery during pregnancy carries maternal mortality of 5โ10% and fetal mortality of 20โ30%. May be necessary for life-threatening IE. Cardiopulmonary bypass is associated with fetal hypoperfusion. Multidisciplinary team must include obstetrics, anaesthesia, and neonatology.
Monitoring: Foetal heart rate monitoring; echocardiography as per non-pregnant guidelines; coordinate care between cardiology, obstetrics, and infectious diseases.
Paediatrics
Epidemiology: IE in children is rare (0.3โ0.5 per 100,000 per year) but increasing with the use of central venous catheters and cardiac surgery. Congenital heart disease is the most common predisposing condition.
Modified Duke criteria: Apply as in adults, with some modification โ fever threshold remains โฅ38ยฐC; peripheral stigmata are less common in children.
Treatment: Antibiotic doses are weight-based (see individual drug cards above). Duration is generally 4โ6 weeks. Gentamicin dosing in children: 2.5 mg/kg IV every 8 hours (monitor levels).
Prophylaxis: Same indications as adults. Ensure all children with congenital heart disease have good dental hygiene and regular dental review.
Elderly
Increasing incidence: Highest rates of IE are in patients aged >65 years. Degenerative calcific valve disease and prosthetic valves are the primary risk factors.
Atypical presentation: May present with delirium, falls, or functional decline rather than classic features. Low threshold for blood cultures in elderly patients with unexplained fever or new heart murmur.
Renal dosing: Gentamicin and vancomycin require careful dose adjustment; eGFR may overestimate renal function in frail elderly โ use measured creatinine clearance. Avoid nephrotoxic combinations when possible.
Surgical decisions: Higher operative risk; frailty and comorbidity should be assessed using validated tools (e.g., Clinical Frailty Scale). Shared decision-making is essential.
Renal Impairment
Common association: Patients on haemodialysis have a 50-fold increased risk of IE, most commonly from S. aureus via dialysis access.
Gentamicin: Extend dosing interval; aim for serum levels as per TDM; consider avoidance if possible (ciprofloxacin or ceftazidime may replace gentamicin for synergy in selected cases โ consult microbiology).
Vancomycin: Dose per AUC-guided approach; significant dose reduction required. Perform TDM before the 4th dose and twice weekly.
Monitoring: Renal function (eGFR, creatinine) at least twice weekly; urinalysis for proteinuria and casts (suggestive of immune-complex glomerulonephritis).
Hepatic Impairment
Flucloxacillin: Hepatically metabolised; use with caution in severe hepatic impairment; consider dose reduction or alternative agent (e.g., cefazolin for MSSA IE, with dose reduction for severe liver disease).
Drug-induced liver injury: Monitor LFTs at baseline and fortnightly; flucloxacillin and rifampicin are hepatotoxic. Discontinuation of suspected offending agent is guided by the RUCAM score and ID advice.
Coagulopathy: Liver disease impairs coagulation; bleeding risk during surgical procedures is increased โ coordinate with haematology and plan perioperative correction of INR, platelets, and fibrinogen.
Immunocompromised
HIV: Risk is increased with low CD4 counts. S. aureus bacteraemia is more common. Atypical organisms (including Candida, Aspergillus) should be considered. Standard antibiotic regimens apply; check drugโdrug interactions with antiretrovirals.
Transplant recipients: Fungal IE (Aspergillus, Candida) is a particular concern. Consider immunosuppression reduction where safe. Standard antibacterial regimens apply for bacterial IE; drug interactions with tacrolimus/ciclosporin (vancomycin, daptomycin โ nephrotoxicity additive).
Diabetes mellitus: Increased risk of S. aureus IE; glycaemic control is important for infection management. Adjust antibiotics for renal function (commonly impaired in diabetes).
Aboriginal and Torres Strait Islander Health
Aboriginal and Torres Strait Islander Health Considerations
Aboriginal and Torres Strait Islander Australians bear a disproportionate burden of infective endocarditis, driven by the high prevalence of rheumatic heart disease (RHD), higher rates of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA), injecting drug use, skin and soft tissue infections, and significant barriers to healthcare access in remote and very remote communities. In the Northern Territory, the age-standardised incidence of IE in Indigenous Australians is estimated to be 5โ10 times higher than in non-Indigenous Australians.
๐ References
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