Infective endocarditis: recognition, prophylaxis, and the GP role

What infective endocarditis is and why it matters

Infective endocarditis (IE) is a microbial infection of the endocardial surface of the heart — most often affecting valves, but also mural endocardium and cardiac implantable electronic devices. In Australia, incidence is approximately six per 100,000 per year, rising with an ageing population, increasing prosthetic valve use, intracardiac device implantation, and ongoing injecting drug use. Most patients with IE will have had multiple general practice contacts during their subacute prodrome before diagnosis is made — making the GP the most important early link in the chain.

Mortality is high — 15–30% in-hospital, 30–40% at one year. Early recognition and urgent specialist referral, not empirical antibiotic treatment in the community, is the GP’s critical contribution.

The clinical scenario that demands high suspicion: unexplained persistent fever in a patient with a cardiac risk substrate — particularly when a new or changing cardiac murmur is present. The classic triad of fever, murmur, and embolic phenomena (stroke, haematuria, back pain, splenic infarct) is the textbook presentation, but many patients present with fever and constitutional symptoms alone for weeks before the diagnosis is made.

A. Core clinical — the AU general-practice framework

Who is at risk

Cardiac substrates for IE:

• Prosthetic cardiac valve — mechanical, biological, or transcatheter aortic valve implant (TAVI); risk persists indefinitely after implantation
• Prior IE — the single greatest risk factor for recurrence
• Rheumatic heart disease (RHD) — disproportionate burden in First Nations Australians, particularly in the Northern Territory, Top End, Kimberley, and Central Australia; managed via RHD Australia state registers
• Unrepaired cyanotic congenital heart disease, or repaired CHD with residual prosthetic material
• Cardiac implantable electronic devices — pacemakers and implantable cardioverter-defibrillators (ICDs)
• Degenerative valve disease — bicuspid aortic valve, mitral valve prolapse with regurgitation — especially in older adults

Exposure risk factors:

• Injecting drug use (IVDU) — right-sided tricuspid valve IE; S. aureus dominant organism
• Recent dental procedures involving gum manipulation or tooth extraction
• Recent invasive procedures — urological, gastrointestinal, gynaecological
• Healthcare-associated bacteraemia — central venous catheters, haemodialysis access, recent surgery

History and symptom recognition

Subacute presentation (days to weeks): Low-grade fever, fatigue, weight loss, night sweats, and malaise out of proportion to apparent illness. Musculoskeletal aching and back pain from immune-complex deposition or vertebral osteomyelitis. Often dismissed as a viral illness for several consultations.

Acute presentation (hours to days): High fever with rigors, rapid clinical deterioration, and early heart failure from acute valve destruction — S. aureus is the dominant organism and accounts for approximately 30% of all IE in Australia.

Embolic symptoms (any timing): Focal neurological deficit from cerebral septic emboli; pleuritic chest pain and haemoptysis from septic pulmonary emboli (right-sided IE in IVDU); haematuria and flank pain from renal infarction; left upper quadrant pain from splenic infarction; limb ischaemia.

Risk history to take: Prior valve disease or prosthetic valve, previous IE, congenital heart disease, RHD, intracardiac device, IVDU (current or historical), recent dental or invasive procedure, recent intravenous line, haemodialysis. Ask specifically about recent antibiotic use — prior antibiotics may blunt blood cultures and create a culture-negative presentation.

Physical examination

• Fever — present in approximately 90% of cases; may be low-grade in subacute presentations
• New or changing cardiac murmur — aortic or mitral regurgitation in left-sided IE; tricuspid regurgitation in right-sided IE (IVDU)
• Heart failure signs — elevated JVP, bibasal crackles, peripheral oedema, gallop rhythm from acute valve regurgitation
• Vascular phenomena: Janeway lesions (non-tender, erythematous macules on palms and soles from septic emboli); conjunctival petechiae; splinter haemorrhages (subungual — non-specific but notable)
• Immunological phenomena: Osler nodes (tender, raised nodules on finger or toe pads — immune complex mediated); Roth spots (retinal haemorrhages with pale centres on fundoscopy)
• Splenomegaly — in subacute disease of several weeks’ duration
• Stigmata of IVDU — track marks, needle-puncture sites, skin abscesses
• Dental assessment — periodontitis, caries, or dental abscess as a potential source for viridans streptococcal IE

GP investigations before referral

When IE is suspected, initiate the following before administering any antibiotic and before arranging transfer:

• Three sets of blood cultures — from different sites, at least 30 minutes apart, each pair aerobic and anaerobic bottles; this is the single most important investigation; organism identification drives four to six weeks of antibiotic choice
• FBC — leucocytosis in acute IE; normocytic anaemia of chronic disease in subacute
• CRP and ESR — elevated; non-specific but useful markers of disease activity
• U&E and creatinine — renal involvement from immune-complex glomerulonephritis or septic emboli
• LFT — baseline before nephrotoxic and hepatotoxic antibiotics
• Urinalysis and microscopy — haematuria and red-cell casts (immune-complex glomerulonephritis); proteinuria
• ECG — PR prolongation or AV block suggests aortic root abscess; ischaemic changes from coronary emboli
• CXR — pulmonary oedema from acute valve regurgitation; septic pulmonary emboli in right-sided IE

Echocardiography is essential but specialist-ordered. eTG complete and the Heart Foundation Australia provide the current AU-specific clinical framework.

B. Diagnosis — the Duke criteria and echocardiography

2023 Duke-ISCVID criteria

The revised Duke-ISCVID 2023 criteria (Fowler et al. Clin Infect Dis 2023) provide the standard diagnostic framework:

Definite IE requires one of: 2 major + ≥1 minor criteria; 1 major + ≥3 minor criteria; ≥5 minor criteria; or pathological confirmation (valve vegetation or abscess on histology or culture from surgery or autopsy).

Major criteria:

1. Positive blood cultures with typical organisms — S. aureus, viridans group streptococci, S. gallolyticus (formerly S. bovis), HACEK organisms (Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella), or Enterococcus faecalis from a community acquisition without identifiable primary focus; or fungi
2. Echocardiographic evidence — vegetation, perivalvular abscess, or new valvular regurgitation on transoesophageal echocardiography (TOE)
3. Imaging (PET/CT) — [18F]FDG-PET/CT or SPECT-CT showing abnormal activity around a prosthetic valve implanted three or more months earlier

Minor criteria: predisposing cardiac condition or IVDU; fever ≥38°C; vascular phenomena (emboli, Janeway lesions, conjunctival haemorrhage, mycotic aneurysm); immunological phenomena (Osler nodes, Roth spots, positive rheumatoid factor); microbiological evidence not meeting major criteria.

Echocardiography

• Transthoracic echocardiography (TTE) — first-line; sensitivity approximately 60–75% for native valve vegetations, lower for prosthetic valves
• Transoesophageal echocardiography (TOE) — sensitivity >90%; required for prosthetic valve IE, intermediate clinical suspicion, non-diagnostic TTE, or suspected complication (abscess, perforation)

Organisms and clinical correlates

Organism	Frequency	Clinical context
Staphylococcus aureus	~30%	Acute, destructive; MRSA increasingly relevant; IVDU and healthcare-associated
Viridans streptococci	~20%	Subacute; dental/oral flora; periodontal disease major risk
S. gallolyticus	5–10%	Subacute; colonoscopy mandatory — 30–50% have colorectal neoplasm
Enterococcus	~10%	GI/GU instrumentation; older patients
HACEK organisms	~3%	Slow-growing fastidious gram-negatives; subacute
Culture-negative	~10%	Prior antibiotic use; Bartonella, Coxiella burnetii (Q fever), Brucella, fungi

C. Treatment and antibiotic prophylaxis

Treatment principles — specialist-led

IE requires prolonged intravenous antibiotic therapy — four to six weeks for native valve endocarditis, up to six weeks for prosthetic valve — under cardiology and infectious diseases specialist co-management. This is not a condition managed from general practice once the diagnosis is established.

The GP’s role in treatment is limited to: taking blood cultures before any antibiotic, facilitating same-day urgent referral, and then supporting long-term follow-up including dental care, RHD secondary prophylaxis, and managing underlying risk factors.

Per eTG complete — Antibiotic v17, empirical treatment before organism identification:

• Native valve, community-acquired: vancomycin IV + ceftriaxone 2 g IV daily — broad cover including MRSA, streptococci, enterococci, HACEK
• Prosthetic valve: vancomycin + gentamicin + rifampicin — extended cover including coagulase-negative staphylococci
• Right-sided IVDU (presumed MSSA): flucloxacillin 2 g IV every four to six hours

Outpatient Parenteral Antimicrobial Therapy (OPAT) via Hospital-in-the-Home (HITH) allows intravenous antibiotic completion in the community for stable, eligible patients. The POET trial (NEJM 2019) demonstrated non-inferiority of an oral step-down in selected stable IE (streptococcal, enterococcal) — endorsed in the ESC 2023 Guideline.

Surgery is required in approximately 50% of IE cases. Indications include: heart failure from severe acute valve regurgitation; uncontrolled infection (perivalvular abscess, persistent bacteraemia after one week of appropriate antibiotics); very large vegetation (>10 mm) with prior embolic event; prosthetic valve dehiscence or abscess; and fungal or Q fever IE.

Antibiotic prophylaxis — who needs it

Routine antibiotic prophylaxis before dental procedures for low- or moderate-risk patients is not recommended per CSANZ 2008 Position Statement, NICE CG64, and the AHA 2007 guideline. The rationale: bacteraemia from normal chewing and toothbrushing exceeds that from dental procedures in cumulative exposure; routine prophylaxis has not been shown to prevent IE in high-quality evidence; and antibiotic resistance and allergy risk are real harms.

Prophylaxis is indicated only for highest-risk groups undergoing dental procedures that breach the gum or oral mucosa:

• Prosthetic cardiac valve — mechanical, biological, or TAVI
• History of prior IE
• Unrepaired cyanotic congenital heart disease, or repaired CHD with residual prosthetic material in the past six months, or with residual defects adjacent to prosthetic material
• Cardiac transplant recipient with valvulopathy
• First Nations Australians with established RHD — an additional Australian-specific category given the disproportionate IE burden in this group per RHD Australia guidance

Regimen: amoxicillin 2 g orally 30–60 minutes before the procedure. If penicillin allergic: clindamycin 600 mg orally.

Not required for: GI, urological, or dermatological procedures in the absence of active infection; low- or moderate-risk valve conditions (mitral valve prolapse without regurgitation, bicuspid aortic valve without prior IE).

D. Australian operations

Hospital and specialist pathway

Suspected IE at general-practice level → urgent same-day cardiology referral via the emergency department, with a direct phone handover to cardiology describing the clinical scenario, risk substrate, and blood culture status. Do not delay transfer to await echocardiography results; take blood cultures first, then arrange transfer.

Tertiary centres in Australia operate Endocarditis Teams per ESC 2023 Class I recommendation — multidisciplinary collaboration between cardiology, cardiothoracic surgery, infectious diseases, microbiology, radiology, and neurology for complex IE.

OPAT / HITH — community intravenous antibiotic completion via a peripherally inserted central catheter (PICC) line under hospital outreach is widely available across Australian states and territories for eligible patients.

RHD Australia and First Nations care

RHD Australia coordinates state-based rheumatic heart disease registers in the NT, QLD, SA, and WA. RHD coordinators support patients requiring four-weekly benzathine penicillin G (Bicillin LA) intramuscular secondary prophylaxis injections. IE is a devastating preventable complication of RHD — register enrolment and adherence to prophylaxis are critical. GPs in regions with First Nations populations should be familiar with register enrolment pathways and culturally safe engagement strategies. Long-distance travel to tertiary cardiology requires care coordination.

Acute rheumatic fever and RHD are notifiable in NT, QLD, SA, and WA. MRSA is notifiable in some jurisdictions per state Communicable Diseases Network Australia requirements.

MBS items

• Items 23 / 36 / 44 — initial and follow-up GP consultations
• Item 11700 / 11701 — 12-lead ECG at the time of assessment
• Item 73807 — blood cultures ordered by GP (laboratory-billed)
• Items 55135–55137 — transthoracic echocardiography (specialist-billed)
• Items 55141–55143 — transoesophageal echocardiography (specialist-billed)
• Items 56301 / 56307 — cardiac CT for perivalvular extension assessment
• Items 707 / 715 — 75+ Health Assessment and Aboriginal and Torres Strait Islander Health Assessment for high-risk monitoring in at-risk populations

PBS

IV antibiotics are administered in-hospital or via OPAT (PBS Section 100 listings for some agents). Oral step-down agents (flucloxacillin, amoxicillin-clavulanate) are General Schedule. Benzathine penicillin G (Bicillin LA) for RHD secondary prophylaxis is available via PBS.

E. Special populations

First Nations Australians. RHD is the dominant IE risk factor in remote and regional Australian communities. Cultural safety, geographic access challenges, and interpreter engagement must be integrated into every clinical contact. RHD coordinators and Aboriginal Health Practitioners are essential partners in secondary prophylaxis adherence and IE education. Warm, supported referrals to tertiary cardiology — with travel and accommodation planning — significantly improve patient engagement.

Patients who inject drugs (PWID). Right-sided tricuspid IE from S. aureus (including MRSA) is characteristic. Harm reduction through opioid agonist therapy (methadone, buprenorphine), needle-syringe programmes, and sterile injecting equipment reduces IE incidence. Withholding surgical management based solely on drug use history is not supported — addiction medicine co-management and re-infection risk reduction through opioid agonist therapy are part of the post-surgical plan. PWID IE carries high re-admission rates; warm referral to addiction medicine is part of the discharge plan, not a condition of surgical access.

Prosthetic valve patients. Early prosthetic valve endocarditis (under 12 months post-implantation) carries high mortality; coagulase-negative staphylococci and S. aureus dominate. These patients require a clear standing communication: any unexplained fever lasting more than 48–72 hours, or fever with new symptoms, warrants same-day blood cultures and urgent assessment — never start antibiotics before cultures are collected. TAVI recipients are an increasing and often older, frailer group with specific procedural risks.

Elderly patients. Degenerative valve disease — bicuspid aortic valve, mitral regurgitation — is the dominant substrate in older adults. Subacute presentations may be subtle; constitutional decline without high fever is common. Drug interactions and renal function must be carefully assessed before prolonged vancomycin or gentamicin therapy.

When to escalate

Suspected IE at any stage → urgent same-day cardiology referral via the emergency department. IE is not managed as an outpatient in general practice.

Before arranging transfer:

• Take three sets of blood cultures from different sites — this is non-negotiable; cultures taken after antibiotics start may be permanently negative
• Do not start empirical antibiotics in general practice without cultures, except when there is haemodynamic instability requiring immediate action

Refer urgently for any of:

• Unexplained persistent fever ≥38°C for more than a few days in a patient with any cardiac risk substrate
• Fever with a new or changing cardiac murmur
• Fever with new focal neurological deficit in a patient with valvular disease or IVDU history
• Fever with haematuria or flank pain in a patient with valvular disease
• Any fever lasting more than 72 hours in a patient with a prosthetic cardiac valve
• Fever with IVDU history

After S. gallolyticus IE: colonoscopy is mandatory post-treatment (30–50% have colorectal neoplasm — do not omit this follow-up step).

RHD register: enrol any newly diagnosed RHD patient in the relevant state register (NT, QLD, SA, or WA) and arrange secondary prophylaxis through the coordinating service.

What this article is and is not

This is general health information about infective endocarditis drawn from current Australian guidelines — eTG complete, RHD Australia, CSANZ 2008, Heart Foundation Australia — and major international evidence including the ESC 2023 Endocarditis Guideline and 2023 Duke-ISCVID criteria. It is not personal medical advice and does not create a doctor–patient relationship. Individual assessment, diagnosis, treatment, prophylaxis decisions, and referral require evaluation by a qualified clinician who knows your circumstances.

For Australian consumer information: HealthDirect, Better Health Channel, Heart Foundation Australia.

For cardiac emergency: 000 (Australian emergency services).

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Sources cited

1. Delgado V et al. ESC 2023 Guidelines for Management of Infective Endocarditis. Eur Heart J 2023;44(39):3948–4042
2. Fowler VG et al. 2023 Duke-ISCVID Criteria for Infective Endocarditis. Clin Infect Dis 2023;77(4):518–526
3. Therapeutic Guidelines (eTG) complete — Antibiotic v17 — Endocarditis
4. CSANZ Position Statement — Endocarditis Prophylaxis 2008
5. RHD Australia — Rheumatic Heart Disease Guidelines
6. Heart Foundation Australia — Heart Conditions
7. Cahill TJ & Prendergast BD. Infective Endocarditis. Lancet 2016;387:882–893
8. Iversen K et al. POET trial — Partial Oral Endocarditis Trial. N Engl J Med 2019;380:415–424
9. NICE CG64 — Prophylaxis Against Infective Endocarditis 2008
10. HealthDirect — Endocarditis
11. Better Health Channel — Heart valve disease